Attempt to speed up Travis builds by using a bundle cache.

Inspired by https://coderwall.com/p/x8exja
Fix .travis.yml
Revert Travis experiments.

This reverts commit ee00d6c402030efa9bce49ff414e88faa3026959.
This reverts commit de2f0e655faeddd443e01921674e47eb8691b4b2.
Add Gemnasium and Code Climate badges.

[ci skip]
Trying out coveralls.io again.
Add coverage badge.

[ci skip]
Fix for spec:coverage:ensure
Bump gem dependencies: capistrano, hipchat, pundit
Fix year in footer.
Bump hdo-storting-importer to 0.3.3
Add magic comment needed for HC notification.
Improve OpenGraph data on issue page
Updated OpenGraph default image.