Remove hearts attribute from Experience model.

Removes ratings from Experience. This is a feature I don't consider
important anymore and I want it out the codebase.
Add RSpec skeleton.

Adds RSpec skeleton and sets the output format to documentation to take
a quick glance at what does which method.
Add Guard gem.

Adds the Guard gem to automate RSpec specs runs.
Add database_cleaner gem.

Adds the database_cleaner gem to ensure clean state for testing.