turn the graph interface into a class
turn the graph interface into a class

I don't know why this was an interface, my bad. Now it's a class with functionality
and everything

Signed-off-by: Sam Phippen <e5a09176608998a68778e11d5021c871e8fae93c@googlemail.com>

samphippen/spe,samphippen/spe,samphippen/spe,samphippen/spe