ASAP (As Straight As Possible) CR-10 filament guide

Hi everyone.

I used to use Greg191134 filament guide or its derivatives for years with great success, so I would like to start by thanking him for his design.
Actually it was my first CR-10 mod!

When trying to print some bamboo or other rugged or sticky filament, the fact that the guide imposes a not so large curvature to the filament did causes some issues with the filament being stuck in the guide even before the extruder.

So I designed this on order to have an as straight path as possible without touching the greasy bar.

You can include a small bit of PTFE, as long as you ensure to work it a bit with a round file to open its entry, and enlarge the oulet.