Merge pull request #2 from nouiz/abergeron-compyte2

Fix a bunch of c_code (that was apparently not tested since there was a bug in the tests).
First working version of gpu sparse.
update to new compyte api
move declaration to global var.
try to find the memory leak
better speed test.
Use new compyte interface.
remove print in c code.
gpu dot(csr, dense), make copy of input matrix less often.
clean up.
Init the cusparse stuff in the init of the python module when possible.
Update speed test code.
Fix the memory leak.

I personally think compyte should handle this correctly, by not reallocating or by decrefing it.
clear the ptr after destroying handler/descripter.
better error message.
move to gpu sparse.Dot(csc, dense)