Remove Devtools

* Remove devtools
* Add Rake
* Add Rubinius specific dependencies
* Add RSpec
  * Use RSpec 2.99 to prepare step to RSpec 3.0
  * Add according rake tasks

In the next commits, re-add the wanted functionality step by step
Code Coverage

* Use the CodeClimate Coverage Reporter
* Remove coverage analysis during the local test runner
* Remove everything from Coveralls