Fix issue with ignore_pyflakes not working.  Essentially it was attempted to update a variable that bottomed out in a static class variable in Checker, so the update wasn't taking.  Thankfully Checker instead has an easy way to solve this by passing our ignore values to the builtins argument, so twas an easy fix.
Merge pull request #119 from jimjkelly/fix/pyflakes_ignore

Fix issue with ignore_pyflakes not working.