Add hash_from_buffer method which accepts byte-likes like memoryview.

[alendit]

Hi,

since the existing functions only accept read-only byte-likes, you have to copy your data, when you working with something like numpy array. With this function you can avoid copies.

[hajimes]

Hi Dimitri,
I apologize for my late response but now I merged your commit into the master branch and confirmed that unit tests passed on Travis CI. Thank you so much for your work!