Compatible with Asset.timestamp

[johnjcamilleri]

Here's my attempt to make Minify work with Asset.timestamp. If the URLs from assetURL contain timestamps then it strips them all out, but remembers the largest one and appends it to the end of the URL to Minify. Possible problems:

1. Is it expensive to use regex here?
2. Not entirely robust, the regex might match even when not using timestamps?