Add RSpec specs to Psychlopedia.

This PR is all about testing, including but not limited to unit and acceptance testing using RSpec and Capybara. I'm aiming to assure basic but effective coverage to the current codebase.

This PR is, and probably will always be, a Work In Progress, but I intend to merge it by #{Date.someday}.
Prefer single-quoted strings when you don't need string interpolation or special symbols.