Big (ridiculos) simple piston fountain pen

It is development of https://www.thingiverse.com/thing:2969193.
The goal was to use biggest o-ring from the set and make a big but still usable pen (for this new features in the pen design was made).

Still all previous versions and future one can be get from https://github.com/sanja-byelkin/SimplePistonPen . I included included snapshot of sources, but you easy can get them by:

`git clone https://github.com/sanja-byelkin/SimplePistonPen.git`

`cd SimplePistonPen`

`git checkout V3`