Add some test data.
Add some basic tests.

(fakeredis has some weirdness around mutability -- it basically uses
 a plain dict to emulate redis, so if you e.g. modify a returned list,
 the changes will be visible to subsequent calls. This is the reason
 for the change in mcbench.client.)
Add fakeredis requirements for tests.
Add simple XPath test.
Fix exceptions inside multiprocessing pool.

Closes #8.
Fix is from here: http://bugs.python.org/issue9400;
need to call super with all the arguments so that self.args
is set properly, so that pickling works properly.