support count hash key

* add functionality 'count_hash_key'
** we can use regex to count_hash_key (same to count_key)
* added unit test related count_hash_key
Update usage for count_hash_key_format
Support count_zset_key_format

* add functionality 'count_zset_key_format'
** same behavior to 'count_hash_key_format', but sum up by zincrby

* added unit test
* updated readme
changed plugin name/version (fluent-plugin-redis-counter -> fluent-plugin-redis-multi-type-counter)
* modify files about license, plugin name