Fix formatting on INSERT (fixes #329)

This patch fixes the formatting on INSERT by creating a new
instance of sql.Values to group all the values.

SQL: insert into foo values (1, 'foo'), (2, 'bar'), (3, 'baz')

Before:
insert into foo
values (1,
        'foo'), (2,
                 'bar'), (3,
                          'baz')

After:
insert into foo
values (1, 'foo'),
       (2, 'bar'),
       (3, 'baz')

1 files changed, 4 insertions, 0 deletions

diff --git a/sqlparse/sql.py b/sqlparse/sql.py
index 2741e83..1f56117 100644
--- a/sqlparse/sql.py
+++ b/sqlparse/sql.py
@@ -621,3 +621,7 @@ class Begin(TokenList):
 
 class Operation(TokenList):
     """Grouping of operations"""
+
+
+class Values(TokenList):
+    """Grouping of values"""