It’s required for FlatCAM to work, and already made its way into the Ubuntu setup script. Added it here too so that people installing using the requirements file also get everything they need.
This simplifies installation on OSX by installing requirements with a single
```pip install -r requirements.txt```
Library minimum versions taken from http://flatcam.org/manual/installation.html#requirements
Where versions have not been specified, requirements.txt reflects this.
Marius Stanciu
Barnaby Walters
Chris Hemingway