Make all tests check for idempotence. fixes #57

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Test fix_raise for a tuple argument
Remove unnecessary check in fix_dict.transform()

Pattern guarantees that there will always be a ‘base’ value.
Don't measure coverage for lines that are precautionary
Fix calls to file()

Closes #43
Use a pre-order search

Should help with the conditional check.
Add a fixer for input() and raw_input()

Combine lib2to3’s input() and raw_input() into a single fixer that uses
six.

Closes #44
Simplify fix_metaclass

Update code for current features of six which simplify parameters for
six.with_metaclass().

Closes #47
Merge pull request #58 from python-modernize/57-check-idempotence

Make all tests check for idempotence. fixes #57
Merge pull request #63 from brettcannon/fix_file

Fix calls to file()
Merge pull request #62 from brettcannon/coverage

Increase test coverage
Add a fixer for open() -> io.open()

Also introduces the concept of opt-in fixers.

Closes #42
Merge pull request #65 from brettcannon/simplify_fix_metaclass

Simplify fix_metaclass
Remove redundant idempotent test
Merge pull request #64 from brettcannon/fix_input

Add a fixer for input() and raw_input()
Rename some variables to be clearer
Merge pull request #67 from brettcannon/fix_open

Add an opt-in fixer for open() -> io.open()