* Update tests to be compatible with jQuery 3.0.0
There was a change in jQuery 3 that ensures that the return value of `.val()` on a multiple select is always an array. This is a breaking change from previous versions, where `null` or `undefined` were returned in these scenarios. Because we cannot `assert.equal` on a list of possible values, these assertions were switched to `assert.ok` which should be good enough.
* Properly strip out units in positioning tests
Before we were assuming that there were no units, and only were we stripping them out if we were expecting 3 digits. Now we just strip out all non-digit characters, so that should do the job and get us what we want.
There was a change in jQuery 3.2.0 that caused the units to be returned in these specific calls. They were not previously being returned, so this was not actually an issue.
* Add automated testing against jQuery 3.4.1
No tests appear to be currently failing.
