Fixing failing Travis.

Also, i have locked the testing version of Ruby for now to 1.9.3. The problem with testing the SDK on multiple versions is that Travis tests them basically in parallel, therefore causing validation errors (e.g. at the same time two ruby test suites create a directory called *test_directory* causing the second one to fail because of the uniqueness validator. Will see what's best to do later.
Hey @ecrisostomo I wrote a comment on this pull request about that issue. Until now the version was locked at 1.9.3 as the lowest version so far. As I would work with other versions also (for other applications) I would bump it up to install it and by accident leave it as is (in the .ruby-version file). Since then, I have gitignored the file and just added it to the .travis-yml file. The thing about Travis is that it is running tests on all 3 versions of Ruby in parallel, and many tests would have directory names such as "test_directory". This would lead to validation errors. I could prefix all of them with the name of the ruby version to avoid this if you want, but I've tested it locally on 1.9.3, 2.0.0 as well as 2.1.1. 
The tests before on Travis were also working only with one version.