Resolve issues with RSpec setup

[spicycode]

With this PR all issues with running tests locally are resolved. Hopefully so for TravisCI as well.

I'll outline the changes I did below.

• Use rspec-rails instead of rspec for Rails projects. See https://github.com/rspec/rspec-rails#installation for details.
• Regenerate default rspec install. This generates different output when rspec-rails is in the Gemfile vs rspec. The command I ran was rails generate rspec:install.
• Require rails_helper, not spec_helper. At some point in recent RSpec versions rails_helper became the default require in test files. spec_helper is required by rails_helper.
• Move to expect syntax (should syntax is deprecated, but still works).
• Remove extra RSpec rake task require (this was causing duplicate test suite runs).

[spicycode]

@fifthbymidwest I'm working through issues with Travis setup now, but that should be the final piece.

[spicycode]

Everything is passing now. Pending your review this is good to merge from my end. (The build failing badge is because master is failing).