Use php.js version_compare function

[wvega]

Use php.js' version_compare function to compare agains jQuery versions in (at least) the following locations:

• https://github.com/wvega/timepicker/blob/master/jquery.timepicker.js#L49
• https://github.com/wvega/timepicker/blob/master/jquery.timepicker.js#L361

This will fix the problem where jQuery 1.10.1 is considered to be older than jQuery 1.4.2, for example.