Add Gemfile.lock as recommended in bundler docs
Merge pull request #98 from jmaupetit/styles-management

Styles management
Merge pull request #96 from jmaupetit/gemfile

Add Gemfile.lock as recommended in bundler docs
Use bundler/bower to manage dependencies

* Add Gemfile[.lock] with proper version constraints
* Add bower.json/.bowerrc
* Configure sass
* Update README
Merge remote-tracking branch 'upstream/gh-pages' into modern-style