Add set_color() convenience method to Spine class
Add set_color method to Patch, to match Collections
Spine is now derived from Patch
use cbook.is_string_like() instead of isinstance() for spines
add cla() support for spines
Update CHANGELOG for removal of old gtk support.
Removed support for gtk < 2.4
improve the animation_blit_qt4 example
Make rcsetup validate_color handle non-string input
fixed a buglet in legend when len(handles)==1 and ncol=2
