Added documentation for the g:syntastic_c_checker option
Revert "python/flake8: add some backwards compat"

This reverts commit 0ef513a0a8f14ad8194a3300ec2563761a1334fe.

The cases that I was trying to catch here were already caught further
along in the errorformat
Merge pull request #567 from Chewie/syntastic_c_compiler

Added documentation for the g:syntastic_c_checker option