Implement pass_arguments parameter for spool* decorators.

Let's say you have a heavily used function or method.  Until now you
had to:
a) change all calls, the spooler dictionary only accepted strings;
b) change the code of your function to read its parameters from a
dictionary and convert them from str.

From now on you just need to add `@spool[forever](pass_arguments=True)` to your
function.
Merge pull request #329 from anaconda/master

Adding my name to CONTRIBUTORS, as requested in #327.
Merge pull request #328 from anaconda/py-spooler-pass-args

[Python] Added option to pass arguments to spooled function