Apply stage1 of futurize

(but removed import of future in setup.py nad limpyd/__init__.py)
Apply stage2 of futurize and apply corrections

Correct with_metaclass calls

Do not inherit from `object`

Use str and bytes from future.builtins

Remove erroneous list() added by futurize

Use decode_responses=True when creating the Redis client
Small pylint/pep8 pass
Optimize iterators for 2.x and 3.x
Bump to version 0.2.0 and add notes about py 3.x