Fix versions for development dependencies (upgrading guard/rspec/spring breaks everything it seems)
Strengthen colors in footer for better lisibility
Paginate API results
Add auditing / versionning to all models with the paper_trail gem
Move paper_trail declaration in Gemfile below rspec so that paper_trail's rspec integration works
Ensure models are versioned
Ensure we don't generate versions for non-interesting changes in User model
Styles: bold keys in shortcuts help modal
Styles: improve link colors
Introduce History model for easier encapsulation of versions
Add a representer for history objects
Add /api/history endpoint to deal with specific items versions
Cleanup specs with the 'versioning' tag provided by paper_trail
Back to paper_trail v3.0.0.beta1 because of a state leak bug in rc1 (see: https://github.com/airblade/paper_trail/issues/293)