Added humans/robots.txt files. Closes #36 and #37.

[Skip CI]
Updated comments in Bootstrap file.

[Skip CI]
Removed profile URL property from the User entity.
Refactored User entity and tests.
Refactored UserLocation entity and tests.
Updated Location entity and tests.
Updated ParentTherapistExclusion entity and tests.
Updated ParentTherapistScore entity and tests.
Updated schedule-related entities and tests.
Added tests for LoginForm.
Updated ProfileEditForm and added tests.
Updated RegisterForm and added tests.
Renamed 'getTherapist' to 'isTherapist'.
Renamed 'getX' to 'isX' for bool fns - more semantic.
Refactored controllers and updated tests.
Updated script to run the tests.
Added a11y test script for certain urls.

Running `scripts/test-pa11y` will spin up a command-line PHP
server and run `pa11y` against the site's public urls.

TODO add tests for users URLs
Passes a11y tests.
Added contrast guidelines to ignore.
Added "remember me" feature.

Closes #39.