Added the abillity to colorize messages.

This includes the following:
- default api for colorization in pyhole.core.color
- Abstract class to define a colormap in pyhole.core.colormap
- A default colormap implementing the mirc syle colors in
  pyhole.core.colormaps.mirccolors

Signed-off-by: Philip Schwartz <philip.schwartz@rackspace.com>