Added support for more memcached operation gets (including hit rate), sets (including ttl), deletes 

Here is the full list of supported metrics 
gets - the number of times on get on that key since mctop started
sets - the number of times on set on that key since mctop started
delete on that key since mctop started
calls - the number of times the key has been called since mctop started (gets+sets+deletes)
hits - hit rate on get requests since mctop started
lifetime - expiration time of the key at the time it was set (ttl)deletes - the number of times on objsize - the size of the object stored for that key
req/sec - the number of requests per second for the key
bw (kbps) - the estimated network bandwidth consumed by this key in kilobits-per-second