Lets use Ruby 2.1
Use bundler version 1.5.1 on travis

- Travis is giving errors with Ruby 2.1
  https://travis-ci.org/codetriage/codetriage/builds/15980297
- Upgrading bundler version solves this issue https://github.com/bundler/bundler/issues/2780
Merge pull request #216 from prathamesh-sonpatki/ruby21

Lets use Ruby 2.1