code update to support passing a new url of json commands at initialization time

I made an implementation using __builtin__ as i was not able to pass arguments to the module using __import__

Normally you have this:
>>> import desir
>>> r=desir.Redis()
>>> len(dir(r))
178
>>>

but using __builtin__ i can force a url to be passed and loaded at importation

>>> import __builtin__
>>> __builtin__.urlCommands="https://raw.github.com/antirez/redis-doc/master/commands.json"
>>> import desir
>>> r=desir.Redis()
>>> len(dir(r))
194

Now with an updated version of the json the Redis class provides more functions.