Removed unused rspec_helper.rb file.

- The related code can be found in the spec/support/kit/helpers.rb.
Refactored use of `pending` to be `skip` instead.

- The use of `pending` is being deprecated.
Refactored `it_also` to simply `also`.
Refactored RSpec support extensions into core and rails specific
extensions.

- Help differentiate and clearly define what extensions are general to
  RSpec and specific to Rails.