Extrusion cooling fan-holder/cowling for MakerFarm Prusa i3 - Version 2

Note: I wound up making a third version that I'm using now. (http://www.thingiverse.com/thing:228536)

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Improved version of my previous fan holder (http://www.thingiverse.com/thing:213416) :

* Mount now has adjustment in 3 axes to accurately position the nozzle.
* Exit nozzle surrounds hot end tip.
* Nut detents in cowling.

Holds a 60x60x10mm fan (I'll probably make a 40x40 adapter).