Update activesupport, i18n and nokogiri gems

The old activesupport gem depended on i18n 0.6.1
Merge pull request #41 from 5apps/security_updates

Update activesupport, i18n and nokogiri gems
Update gitignore
Update Sinatra to 1.4.5

Also update backports package, its current version is causing issues on
Ruby 2.1.3
Run specs on Travis on Ruby 2.1.3 as well as 1.9.3

Also use bundler to run the specs
Merge pull request #45 from 5apps/update_sinatra_and_backports

Update Sinatra to 1.4.5

Sinatra 1.4.4 and 1.4.5 have memory improvements (fixed leaks and less allocated objects per request)

Also update backports package, its current version is causing issues on
Ruby 2.1.3
Use new hook-juggler URL in Travis config

Heroku changed their routing using a new domain.
Run tests on Travis using latest Ruby 2.1