Fixes broken test introduced by #61

[jelhan]

Test was broken since it was introduced by #61. Have to call .datepicker('update') to notify about changes.

I'm still not convinced about this test. It seems like testing bootstrap-datepicker and not this addon. But lets get a working testing suite again first.

[soulim]

@jelhan you rock! 😄 👍

[octronic]

This test was originally introduced with #35 (which solved #33)

With #63 it was refactored into an integration-test (see: 2c0ca2f)

But this test was removed with 7c53cf0

Long story short: my guess is #61 added this test again by accident.

[soulim]

Thanks for the investigation @octronic! 😉👍