Fix for target double click 'bug'

In some browsers clicking on the target (`a.select-list`) twice in quick succession causes the dropdown list to then open and close immediately rendering the dropdown list impossible to use. It seems to be because the focus and blur events get a bit mixed up.

I've added a simple boolean check that doesn't allow `a.select-list` to be clicked again unless the dropdown list has triggered the blur event.

I've tested this in the following browsers:

**OS X**
Chrome 27
Safari 6
Firefox 20

**Windows XP**
Chrome 26
Firefox 16
IE 7 & 8