Rename package to just GraphBLAS.jl

[ViralBShah]

This name is quite a mouthful.

[rayegun]

Haha I believe you called me off of the rename originally :P

We can do that. It's the only expected implementation for a while, and it is mostly spec conformant so eventually swapping out the backend shouldn't be difficult.

I'll get ready to tag a new release and then change the name.

[ViralBShah]

I know it was me. But It doesn't look like other implementations are happening anytime soon :-)