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, 9 insertions, 8 deletions

diff --git a/spec/hashie/mash_spec.rb b/spec/hashie/mash_spec.rb
index 1a0ad4f..680f403 100644
--- a/spec/hashie/mash_spec.rb
+++ b/spec/hashie/mash_spec.rb
@@ -184,7 +184,8 @@ describe Hashie::Mash do
         details: {
           email: 'michael@asf.com',
           address: 'Nowhere road'
-        })
+        }
+      )
     end
 
     describe '#deep_update' do
@@ -284,7 +285,7 @@ describe Hashie::Mash do
       end
 
       it 'leaves only specified keys' do
-        expect(subject.keys.sort).to eq %w(details middle_name)
+        expect(subject.keys.sort).to eq %w[details middle_name]
         expect(subject.first_name?).to be_falsy
         expect(subject).not_to respond_to(:first_name)
         expect(subject.last_name?).to be_falsy
@@ -386,28 +387,28 @@ describe Hashie::Mash do
     end
 
     it 'responds to a set key with a suffix' do
-      %w(= ? ! _).each do |suffix|
+      %w[= ? ! _].each do |suffix|
         expect(subject).to be_respond_to(:"abc#{suffix}")
       end
     end
 
     it 'is able to access the suffixed key as a method' do
-      %w(= ? ! _).each do |suffix|
+      %w[= ? ! _].each do |suffix|
         expect(subject.method(:"abc#{suffix}")).to_not be_nil
       end
     end
 
     it 'responds to an unknown key with a suffix' do
-      %w(= ? ! _).each do |suffix|
+      %w[= ? ! _].each do |suffix|
         expect(subject).to be_respond_to(:"xyz#{suffix}")
       end
     end
 
     it 'is able to access an unknown suffixed key as a method' do
       # See https://github.com/intridea/hashie/pull/285 for more information
-      pending_for(engine: 'ruby', versions: %w(2.2.0 2.2.1 2.2.2))
+      pending_for(engine: 'ruby', versions: %w[2.2.0 2.2.1 2.2.2])
 
-      %w(= ? ! _).each do |suffix|
+      %w[= ? ! _].each do |suffix|
         expect(subject.method(:"xyz#{suffix}")).to_not be_nil
       end
     end
@@ -560,7 +561,7 @@ describe Hashie::Mash do
     end
 
     it 'includes all keys' do
-      expect(mash.to_hash.keys).to eql(%w(outer testing))
+      expect(mash.to_hash.keys).to eql(%w[outer testing])
     end
 
     it 'converts keys to symbols when symbolize_keys option is true' do