Update Rubocop and address the addressable todos

This is a big step forward in our Rubocop setup. I addressed all of the todos
from the current version of Rubocop that made sense to. The only things that
remain are metrics and one cop that relies on the line length metric to work.

I made some judgment calls on disabling a few cops:

1. The `Layout/IndentHeredoc` cop wants you to either use the squiggly heredoc
   from Ruby 2.3 or introduce a library. Since we are a low-level library that
   is used as a transitive dependency, we cannot introduce another library as a
   dependence, so that option is out. Also, we support Rubies back to 2.0
   currently, so using the squiggly heredoc isn't an option. Once we remove
   support for Rubies older than 2.3, we can switch to the squiggly heredoc cop.
2. The `Naming/FileName` cop was reporting false positives for a few files in
   the repository, so I disabled it on those files.
3. The `Style/DoubleNegation` cop reports lints on a few cases where we use
   double negation. Given the very generic nature of Hashie, the double-negation
   is the easiest, clearest way to express that we want an item to be a Boolean.
   I disabled the cop because we exist in the gray area where this makes sense.

1 files changed, 21 insertions, 21 deletions

diff --git a/lib/hashie/mash.rb b/lib/hashie/mash.rb
index d995138..bc5873c 100644
--- a/lib/hashie/mash.rb
+++ b/lib/hashie/mash.rb
@@ -61,7 +61,7 @@ module Hashie
     include Hashie::Extensions::PrettyInspect
     include Hashie::Extensions::RubyVersionCheck
 
-    ALLOWED_SUFFIXES = %w(? ! = _)
+    ALLOWED_SUFFIXES = %w[? ! = _].freeze
 
     class CannotDisableMashWarnings < StandardError
       def initialize(message = 'You cannot disable warnings on the base Mash class. Please subclass the Mash and disable it in the subclass.')
@@ -74,7 +74,7 @@ module Hashie
     # @api semipublic
     # @return [void]
     def self.disable_warnings
-      fail CannotDisableMashWarnings if self == Hashie::Mash
+      raise CannotDisableMashWarnings if self == Hashie::Mash
       @disable_warnings = true
     end
 
@@ -99,9 +99,9 @@ module Hashie
       @_mashes ||= new
 
       return @_mashes[path] if @_mashes.key?(path)
-      fail ArgumentError, "The following file doesn't exist: #{path}" unless File.file?(path)
+      raise ArgumentError, "The following file doesn't exist: #{path}" unless File.file?(path)
 
-      parser = options.fetch(:parser) {  Hashie::Extensions::Parsers::YamlErbParser }
+      parser = options.fetch(:parser) { Hashie::Extensions::Parsers::YamlErbParser }
       @_mashes[path] = new(parser.perform(path)).freeze
     end
 
@@ -114,7 +114,7 @@ module Hashie
       end
     end
 
-    alias_method :to_s, :inspect
+    alias to_s inspect
 
     # If you pass in an existing hash, it will
     # convert it to a Mash including recursively
@@ -125,10 +125,10 @@ module Hashie
       default ? super(default) : super(&blk)
     end
 
-    class << self; alias_method :[], :new; end
+    class << self; alias [] new; end
 
-    alias_method :regular_reader, :[]
-    alias_method :regular_writer, :[]=
+    alias regular_reader []
+    alias regular_writer []=
 
     # Retrieves an attribute set in the Mash. Will convert
     # any key passed in to a string before retrieving.
@@ -149,8 +149,8 @@ module Hashie
       regular_writer(key, convert ? convert_value(value) : value)
     end
 
-    alias_method :[], :custom_reader
-    alias_method :[]=, :custom_writer
+    alias [] custom_reader
+    alias []= custom_writer
 
     # This is the bang method reader, it will return a new Mash
     # if there isn't a value already assigned to the key requested.
@@ -183,26 +183,26 @@ module Hashie
       super(*keys.map { |key| convert_key(key) })
     end
 
-    alias_method :regular_dup, :dup
+    alias regular_dup dup
     # Duplicates the current mash as a new mash.
     def dup
       self.class.new(self, default, &default_proc)
     end
 
-    alias_method :regular_key?, :key?
+    alias regular_key? key?
     def key?(key)
       super(convert_key(key))
     end
-    alias_method :has_key?, :key?
-    alias_method :include?, :key?
-    alias_method :member?, :key?
+    alias has_key? key?
+    alias include? key?
+    alias member? key?
 
     # Performs a deep_update on a duplicate of the
     # current mash.
     def deep_merge(other_hash, &blk)
       dup.deep_update(other_hash, &blk)
     end
-    alias_method :merge, :deep_merge
+    alias merge deep_merge
 
     # Recursively merges this mash with the passed
     # in hash, merging each hash in the hierarchy.
@@ -213,15 +213,15 @@ module Hashie
           custom_reader(key).deep_update(v, &blk)
         else
           value = convert_value(v, true)
-          value = convert_value(blk.call(key, self[k], value), true) if blk && self.key?(k)
+          value = convert_value(yield(key, self[k], value), true) if blk && key?(k)
           custom_writer(key, value, false)
         end
       end
       self
     end
-    alias_method :deep_merge!, :deep_update
-    alias_method :update, :deep_update
-    alias_method :merge!, :update
+    alias deep_merge! deep_update
+    alias update deep_update
+    alias merge! update
 
     # Assigns a value to a key
     def assign_property(name, value)
@@ -263,7 +263,7 @@ module Hashie
       method_name.end_with?(*ALLOWED_SUFFIXES) && key?(method_name.chop)
     end
 
-    def method_missing(method_name, *args, &blk)
+    def method_missing(method_name, *args, &blk) # rubocop:disable Style/MethodMissing
       return self.[](method_name, &blk) if key?(method_name)
       name, suffix = method_name_and_suffix(method_name)
       case suffix