Legs for air vent mounting

Made these simple legs in order to use [ByteSlinger's OnePlus 3 phone holder](http://www.thingiverse.com/thing:1742323) in my car's air vent instead of a Brodit mount it was designed for. So far I've used this in three different vehicles with very different air vent designs, and surprisingly it has worked beautifully with each.

Be careful with installation, mounting can damage the air vent or the vent blades, which I take no responsibility over.