Pull request

I've added a couple minor features:

1. A check to make sure that the ones matrix is large enough to do a particular sum.
2. A keyword argument to set the size of the ones matrix during cublas_init if desired.
3. More detailed cublas error reporting (which mirrors the cublas errors in CUDA 6.0)
Hmm, that opens a whole new can of worms.  Using peek and then check seems like a hack or stopgap.  It seems like transparent error reporting should be architected in better from the beginning.  I'll think about a way to do this better.  Maybe you have some suggestions?  

The original reason I started down this path was that "CUBLAS_ERROR" was definitely not descriptive enough.  The main thing I wanted to come through clearly was when allocs fail because we're out of memory.  

Now what I debating between is return error strings to Python or returning error codes.  Since the CUDA error codes overlap with the CUBLAS error codes, if we use error codes, we'll have to create our own, or deal with that in some other way.