CRC and other hash algorithms

[bblanchon]

@supergohan, in #18, you requested a CRC feature in StreamUtils.

That's something I wanted to add for a long time, but I waited for an actual application to make sure the interface was designed correctly.

Can you share a (pseudo-)code sample that shows how you plan to use this feature? I'm assuming that you're using this hash to control the integrity of a message; make sure that you include this part in the sample.