Merge branch 'hotfix/2.5.1'

* hotfix/2.5.1:
  * Rails 4.0.2 * Rails 3.2.16
Merge branch 'release/2.6.0'

* release/2.6.0:
  * Bootstrap v3.0.3 * Respond.js 1.4.1 * Submodules locked to tags instead of master branch
Merge branch 'release/2.7.0'

* release/2.7.0:
  I mean... remove Gemfile.lock! [ci skip]
  Do not check Gemfile.lock [ci skip]
  * Updated README * Updated CONTRIBUTING guidelines * Added .editorconfig [ci skip]
  * [dev] Removed active_record from dummy test application * [dev] Removed debugger and sqlite dependency
  Respond.js 1.4.2
  Support for ruby 2.1
  Updated gems Improved test helper
* Fixed license SPDX ID in gemspec
Merge branch 'hotfix/2.7.1' into develop

* hotfix/2.7.1:
  * Fixed license SPDX ID in gemspec