Removes rubies that have been end of life'd

Ruby 1.8.7 - http://www.ruby-lang.org/en/news/2013/06/30/we-retire-1-8-7/
REE - http://blog.phusion.nl/2012/02/21/ruby-enterprise-edition-1-8-7-2012-02-released-end-of-life-imminent/

Rubinius doesn't say anything, but whatever, let's remove all 1.8
support.

Also moves the CI and Code Climate details to the top of the readme
Merge pull request #760 from Shopify/travis/remove_end_of_lifed_rubies

Removes rubies that have been end of life'd