Using Doctrine\Common\Persistence classes.

Using Doctrine\Common\Persistence classes (ObjectManager and ObjectRepository)
in place of Doctrine\ORM classes (EntityManager and EntityRepository).
Fixed page titles site-wide.

Updated the page titles site-wide to reflect the actual content
of the page. Also added the description meta field which is empty for now,
but needs to be filled in with the appropriate copy.
Added the ability to remove availabilites from schedule.

Rundown of changes:

- `getAvailability()` is now `isAvailabile()`, the latter reads better.
- Cleaned up error messages.
- Added error messages to the schedule view.
- Touched up styles for new form elements.
- Refactored Schedule* entity tests to use new methods name.

Closes #35.
Fixed box-sizing issue.
Added browser support to the README file.

Closes #27.
Added a bit more context to the contributing file.
Removed unneeded namespace imports.
Added script to create a test user acct.
Updated database script.
Renamed unit tests script.
Updated pa11y script.

Closes #32.

Workflow for running complete test suite:

- scripts/database
- scripts/test

Creates the database, inserts a test user, runs PHPUnit, and runs pa11y.
Added colophon and sponsors page.

Closes #46 and closes #51.

Currently both pages are just stubs, and still need to be filled with content.
Hide/show passwords on demand.

Closes #43.

Passwords can now be shown then hidden on demand. Passwords are still hidden
by default.
Updated a11y test script.
Refactored ScheduleHelper.
Passing a11y tests.
Updated test scripts.