Adding moar badges

Adding these badges:

  - [![Gem Version](https://badge.fury.io/rb/sidekiq.png)](https://rubygems.org/gems/sidekiq)
  - [![Code Climate](https://codeclimate.com/github/mperham/sidekiq.png)](https://codeclimate.com/github/mperham/sidekiq)
  - [![Build Status](https://travis-ci.org/mperham/sidekiq.png)](https://travis-ci.org/mperham/sidekiq)
  - [![Dependency Status](https://gemnasium.com/mperham/sidekiq.png)](https://gemnasium.com/mperham/sidekiq)
  - [![Coverage Status](https://coveralls.io/repos/mperham/sidekiq/badge.png?branch=master)](https://coveralls.io/r/mperham/sidekiq)