Update redis_natives/datatypes.py

ZSet() improvements  (faster __contains__, added ZREVRANGEBYSCORE, ...)
Updated Primitive members to include __le__, __lt__, etc..

also fixed __eq__ so that when a Primitive is a number X, it will return true when compared to both x and 'x'
Merge pull request #2 from srj55/patch-1

+ ZSet() improvements  (faster __contains__, added ZREVRANGEBYSCORE, ...)
+ Updated Primitive members to include __le__, __lt__, etc. also fixed __eq__ so that when a 
   Primitive is a number X, it will return true when compared to both x and 'x'