Removes support for basic authentication.

This functionality can easily be implemented as needed in custom feature
contexts.
Renames Drupal to DrupalDriverManager.
Enabling some d8 tests.
Merge pull request #70 from jhedstrom/driver-manager-refactor

Renames Drupal to DrupalDriverManager.
Merge pull request #69 from jhedstrom/remove-basic-auth

Removes support for basic authentication.