ibuffer-perspective

Adds functionality to ibuffer for grouping buffers by their current
perspective.  See http://github.com/nex3/perspective-el for information on
emacs perspectives.

Note: this functionality is extremely limited. It simply categorizes the
ibuffer list via perspective. You can not easily change a buffer's
perspective via ibuffer mode at this time. Most likely, this program will
not be expanded on account of the original author's infrequent use of
perspective mode.

This was modelled off of ibuffer-vc. See
http://github.com/purcell/ibuffer-vc