RESULT_SEVERITY: Add tests
ConsoleOutputter: Mark _print_result translatable
ConsoleOutputter: Allow redirection to file
ConsoleOutputter: Add special case for file=None
ConsoleOutputter: Test print_result too
OutputterTest: Test LineResult on print_result too
BearRunnerTest: Fix invalid length check

https://github.com/sils1297/coala/issues/105
gitignore: Add coverage.xml
FileCollector: Remove unneeded brackets
ResultTest: Remove unneeded setUp()
README: Add gitter badge