Retire use of pango

[jondkelley]

Probably dead in gtk3. It's used to do Cairo front rendering and stuff?

https://sites.google.com/site/randomcodecollections/home/python-gtk-3-pango-cairo-example

Sources of review:

d_rats/ui/main_chat.py
29:import pango

d_rats/ui/main_messages.py
30:import pango

d_rats/spell.py
130:    import pango

d_rats/formgui.py
35:import pango

d_rats/miscwidgets.py
25:import pango

build/lib/d_rats/ui/main_chat.py
29:import pango

build/lib/d_rats/ui/main_messages.py
30:import pango

build/lib/d_rats/spell.py
130:    import pango

build/lib/d_rats/formgui.py
33:import pango

build/lib/d_rats/miscwidgets.py
23:import pango```