http://github.com/defunkt/pystache/commit/6372a33744ae149a1c0f5de6d42bbb763381962b#comments

Assigning a default context argument  actually creates a global, which I don't think was the intended effect.  More discussion and a better explanation of this can be found at http://bit.ly/1iw46

change it to a single function. Also update the
tests