Fixed some API differences between python-memcached and pymemcache.
Don’t use the options dict if it’s `None`.
Added LICENSE and README.rst file.
Removed redundant check if server parameter is string as done upstream already.
Added pymemcache to install requirements.
Fixed some copypasta.
Merge pull request #2 from jezdez/api-fixes

Fixed compatibilit and API as well as packaging issues.