Added config option #context.
It defines optional sub-directory in which rails app is deployed. By default Rails.application.config.relative_url_root is used.

It allows to run specs on URLs like http://localhost:3000/my_app/teaspoon.
Teaspoon.configuration.context should be set to nil by default, then it can be overridden in engine unless user set it earlier
Merge pull request #133 from kowal/rails-relative-url-root-fix

Added config option #context.