Add missing iPad Air and iPad Mini models

[antoinevg]

Added entries for the iPad Air, iPad Air 2, iPad Mini and iPad Mini 3 models.

Also fixed a potential bug where the device detection timeout callback would cause ios-deploy to shut down even if the device had been found.

[shazron]

Stealth second commit in there when the issue is about adding new iOS device models, but I'll allow it this time :) Filed #244

[shazron]

(what I meant was, one PR per issue -- just in case we need to backtrack one fix)

[antoinevg]

Thanks @shazron, my apologies! :-)