Open-hanging spool-holder

Yes, another spool... but I wanted a spool that was:

-open on one side (to easy changing of the filament, like this clever one http://www.thingiverse.com/thing:8317)
-parallel to the x-axis (more direct move for the filament)
-hanging from the top (like the http://www.thingiverse.com/thing:3962 used before)
-quick and easy to mount/unmount for when carrying the reprap
-and even flat transportable if possible

I'm testing it right now, and it seems ok :)