Removing todo for now to get readthedocs building.
Introduces a raw Drupal context.
Moving entity management to raw context.
Removes unused classes.
Moves classes to the raw context.
Docs.
Further separate raw drupal context from Mink Extension.

- Splits drush command support into a separate context
- Extends the raw mink context instead of the full mink context
- Use of the Mink Extension is still supported by adding it in
  `behat.yml`.
- The Drush command steps must also be added in `behat.yml`.
Move Mink Extensions into a separate context.

- Splits all non-Drupal-specific step definitions into a
  `WebHelperContext`. This context directly extends the Mink Extension,
  so it should be used whenever Mink Extension steps are needed.
Updating the README.
Don't rely on the Mink Extension in Drupal context.
Move message steps into a separate context.
Enabling translation on additional contexts.
Renames web helper context to MinkExtension for clarity.
Allow multiple roles to be added to a user.

- See commit bb437f1.
Move login/logout methods to the raw context.
Extract logic to `loggedInWithRole()`.
Use `--strict` for running behat on travis.
Fix the drush output to throw a proper exception.