refactor and add tests to tailing
fix regression when going below the log zone

Since a431b68c2858a2d96f35accfe577497344de98a2, when going below the max
of the log files, the position button would remain in fixed position.
This fixes it.
Merge pull request #233 from dmathieu/tailing

Refactor tailing and test it
Remove `mailto:` URLs

Addresses https://github.com/travis-ci/travis-ci/issues/1807
Remove Bundler patch

The patch does not seem necessary any longer.
Remove urlAuthor and urlCommitter fields

No longer in views, so no need to keep these.
Merge pull request #238 from travis-ci/ha-bug-gemfile_fix

Remove Bundler patch
Merge pull request #237 from travis-ci/ha-bug-gh_core_1807

Remove `mailto:` URLs

Closes travis-ci/travis-ci#1807.
Fix typo in Code Climate popup.