`selectOnClose` is a new option which works very much like the old
`selectOnBlur` option. When the `close` event is triggered, the
highlighted result is automatically selected. This is useful for
single selects, which is where it is designed to be used, but it
can also be used on multiple selects.
This also adds tests to verify that this works in the future.
During the creation of the test, we noticed that we were missing a
mock container that could be used for triggering events. One was
created and a general mock JS file was created to hold any future
mocks for tests.
