Added src folder, init file, and mutable.py

Signed-off-by: Nathan <nzhang32@gmail.com>
Updated mutable.py, added preliminary tests.  Does not work yet

Signed-off-by: Nathan <nzhang32@gmail.com>
Instantiating Proxy(type) actually works.  magic methods don't though.

Signed-off-by: Nathan <nzhang32@gmail.com>
renamed mutable.py to proxy.py

Signed-off-by: Nathan <nzhang32@gmail.com>
Edited to reflect new format