tests for zincrby, zcount, zcard, zadd
fix type converter
zrangebylex, zrange, zlexcount commands
move convert_to_int_or_float to SortedSetCommandsMixin
pep8
Merge pull request #28 from jettify/feature-sorted-sets1

tests for  	zrangebylex, zrange, zlexcount, zincrby, zcount, zcard, zadd