Incremental release

NEW:

• Add hmset_dict command
  (see #130);
• Add RedisConnection.address property;
• RedisPool minsize/maxsize must not be None;
• Implement close()/wait_closed()/closed interface for pool
  (see #128);

FIX:

• Add test for hstrlen;
• Test fixes

MISC:

• Enable Redis 3.2.0 on Travis;
• Add spell checking when building docs
  (see #132);
• Documentation updated;