'db' and 'type' are optional. 'db' stands for ledis db index, ranges from 0 to 15, its default value is 0. 'type' is a custom content type, can be json, bson or msgpack, json is default.
'return_value' stands for the output of 'cmd', it can be a number, a string, a list, or a hash. If the return value is just a descriptive message, the second format will be taken, and 'success', a boolean value, indicates whether it is successful.
####Example
#####Curl
curl http://127.0.0.1:11181/SET/hello/world
→ {"SET":[true,"OK"]}
curl http://127.0.0.1:11181/0/GET/hello?type=json
→ {"GET":"world"}
#####Python
Requires [msgpack-python](https://pypi.python.org/pypi/msgpack-python) and [requests](https://pypi.python.org/pypi/requests/)