Add "max_ones" argument to cublas_init + PEP8 cleanup

* Adds a 'max_ones' argument to cublas_init that configures the size of the 'ones' array that is used to compute sums via matrix multiply.  
* Also removes some unnecessary spaces on blank lines.

For now let's just do the max-ones feature, and leave the error reporting thing that was started in #29 for another day.


`cm.cublas_init()` is the high-level Python routine, it doesn't return anything and raises an exception by itself already!