fix issue #224

This PR fixes issue #224 which was caused by the fact that some browsers raise a 'change' event before the 'click' event - and as click was used to synchronize the data model, the 'change' callback received an invalid value. The fix was not easy to reproduce in a test environment so I updated hashtester to reproduce this behaviour.

Note: apart from firefox, I don't know which browser implement the 'change' before 'click' behaviour - so hashtester may have to be updated for all tests to pass (which is unfortunate as the fix is really simple)