Hopefully fix travis ci
Hopefully fix travis ci

In the logs it says that `rake` specified in gemspec file doesn't match the one installed in travis.
hugopeixoto/simplecov,colszowka/simplecov,ptashman/simplecov,gerry3/simplecov,QuickPay/simplecov,colszowka/simplecov,irfanah/simplecov,playpasshq/simplecov,mallikarjunayaddala/simplecov