Allow passing of parameter for variable initialization

[randomrandom]

Allow passing of an opt parameter for variable initialization (scale) in the conv1d, aconv1d, embed, etc. methods (can be found here: https://github.com/buriburisuri/sugartensor/blob/master/sugartensor/sg_layer.py).

Currently those methods are automatically using he_uniform, with assumed scale of 1. This causes problems on large shaped objects, e.g. at some input / outputs I get scale of 0.005 for the uniform method, which causes the network to misbehave and dead neurons to appear (gradients close/equal to 0).

There's no other trivial way to change the initialization methodology except editing the library code.