setting up helper libraries.
Adds a test suite via RSpec

* Adds RSpec to test functionality.
* Refactors gem into a namespaced environment to avoid collisions.
* Renames base class to `RailsDatatables::Base`.
* Edits base hook methods the base class provides.
* Edits default generator to `DatatableGenerator`. Can be invoked with:
  `$ rails generate datatable NAME`
Merge pull request #1 from antillas21/setup

Setup