Improve jquery migrate and jquery mobile detection (#2145)

* Improve jquery migrate and jquery mobile detection

This can be tested [here](http://docs.python-requests.org/en/master/)

- remove the `rc` thingy, since no other patter using it, and I haven't seen a
single website actually using it.
- jquery-migrate is valid too
- Remove `.*` in favour of of an optional `.min`

* Fix an unnecessary escape, thanks to @gadcam