Add new key bits to get data for positional and keyword method args.
Allow arguments to ArgsKeyBit and KwargsKeyBit to select subset of args.

Also added tests and documentation.
Merge branch 'master' into add-args-kwargs-bits
#36: if no param names passed to KwargsKeyBit use all kwargs for key
#36: add test case for KwargsKeyBit if no parameters given

Assert that KwargsKeyBit generates key bit using all kwargs.
#36: added documentation to markdown help and Release Notes
#36: moving new key bit doc to just below HeadersKeyBit

per @chibisov’s instructions.
Merge pull request #43 from nofeet/add-args-kwargs-bits

Add args and kwargs key bits