[TASK] Switch from Ruby 2.1.0 to 2.1.1 in Travis.

The latest Ruby 2.1 version provided by Travis is 2.1.1.

We should switch to it.
Merge pull request #36 from braingourmets/task/ruby-2.1.1

[TASK] Switch from Ruby 2.1.0 to 2.1.1 in Travis.