Clarify notes on supported GNU Emacs versions
Fix expected Go error message on Travis CI
Remove superfluous docstring
Expect failures if checkers are missing

Some syntax checkers fail to install on Travis CI or Vagrant, so we
should expect test failures if the syntax checker is missing, regardless
of the testing environment
Run all tests on Travis CI
Revert "Run all tests on Travis CI"

JRuby and Scala tests still fail on Travis CI, for whatever reason.

This reverts commit 33d81a90a0bbdb331fe34caea569ffdd1f4c32b0.
Update changelog
Remove unused test resources
Fix mocker requirements
Refactor error navigation tests

Make test cases more granular