First working version; very shaky

Depends on Fugitive and (optionally, but required for color) AnsiEsc and
also on the user having the appropriate aliases in their Git
config---which is the part that's very shaky
Improved design as complained of in last commit

Removed direct dependency on Fugitive, though the intention is still to
fit in with its suite of commands

You must :call ggraph#configure() the first time you use it.
Make git graph load silently in own nowrite buffer

+ Make sure commands are executed silently, for smoother workflow
+ Make sure graph is loaded in its own buffer
+ Make sure that contents of last graph command are not appended
+ Make sure that AnsiEsc is not toggled on and off
Merge branch 'master' of github.com:Kazark/vim-ggraph
Sketched out README