[WIP] Implementing Averaged SGD

Working on implementing averaged SGD for both classifier and regressor for #543
right, looking at my own code [1] it seems like I started counting with one finger (not zero) -- but if ``T==1`` is will give you a zero weight vector... 

[1] https://github.com/pprett/bolt/blob/master/bolt/trainer/avgperceptron.pyx#L138