Updates schema

* Removes ON CONFLICT FAIL since ABORT is both the default behavior and
the SQL standard behavior
* Adds unique index to day column
Reformats schema.sql
Shuffles config arrays for user convenience
Adds phpunit as dev dependency
General comment, formatting, and namespace cleanup
Changes require_once to require for autoloader
Adds findFirstImage()
Adds tests to cover unique indices, test for findFirstImage()