Upgrade MobileDetect library to 2.7.1

[Aaron Wells]

This is the library we use for device detection. It's currently on 2.0.9, which is pretty old considering how swiftly the landscape of mobile devices changes.

[Aaron Wells (u-aaronw)]

As noted on https://github.com/serbanghita/Mobile-Detect , this library updates pretty frequently to reflect the frequent changes in mobile devices out there. So, it may be a good idea to update this more frequently ourselves, and possibly backport the updated library to the stable releases.

[Aaron Wells (u-aaronw)]

https://reviews.mahara.org/2673

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/2673
Committed: http://gitorious.org/mahara/mahara/commit/a08539dad567086f3f14694f112819796b5fc3d2
Submitter: Aaron Wells (<email address hidden>)
Branch: master

commit a08539dad567086f3f14694f112819796b5fc3d2
Author: Aaron Wells <email address hidden>
Date: Thu Oct 31 16:53:42 2013 +1300

Update MobileDetect to 2.7.1

Bug 1246576

Change-Id: I13b6499eae6697cd0341be73c133984ba61ffc1e