Add note about python-dev and libffi-dev.
Add note about python-dev and libffi-dev.

Weasyl/misaka,Weasyl/misaka,FSX/misaka,Weasyl/misaka,FSX/misaka,lepture/misaka,Weasyl/misaka,lepture/misaka,FSX/misaka,Weasyl/misaka,lepture/misaka,FSX/misaka