Fix typo in README.md.

Fixed typo.

You might be wondering what a "snakebaset" is, and at first I did as well, but then I decided it must be a kind of reptilian companion to [Baset](http://en.wikipedia.org/wiki/Bastet), a female cat goddess.

After being incredibly entertained by Wikipedia in a path that ultimately brought me [back to Philosophy](http://flowingdata.com/2011/06/08/all-roads-lead-to-philosophy-on-wikipedia/), I realized it likely had a much simpler explanation:

It should be **snakebasket**.