Increase version number to 0.2.0

[cfournie]

Let's cut a feature release that includes these feature-adding PRs:

• Restrict list comprehension complexity Restrict list comprehension complexity #30
• Use simple lambdas Use simple lambdas #31
• add new check for multiple imports add new check for multiple imports #24
• Check that we disable pylint messages by name and not code Check that we disable pylint messages by name and not code #34
• Utility to detect changed python files Utility to detect changed python files #28
• Renumber messages as C60 Renumber messages as C60 #35
• Help messages don't support formatting Help messages don't support formatting #23
• Add try/except/finally complexity rules Add try/except/finally complexity rules #12