Prusa i3 circular fan with inductive sensor support

New improved version http://www.thingiverse.com/thing:2068697

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This is a remix of mcleishn's " HICTOP fan nozzle cooler Filament". I really liked the design however I wanted to make some improvements for myself, Figured I should share :)

Improvements:

* Added a mount for an inductive sensor 4mm to the side of the backet
* Added some extra support to the bracket to make the arm attaching the vent stronger
* Made the top layer of the circular duct bigger