Fix TypeError when handling multi exception

When errors occurs using multi/exec, avoid "TypeError: Cannot read property 'length' of undefined"
updated RedisClient.prototype.hmset to accept string or numeric keys when calling client.hmset(key, {key1: val1, key2: val2})
removed trailing whitespace
added tests for HMSET using numeric key
restored white space
fixed spacing issue
Merge branch 'master' of https://github.com/kwangsu61/node_redis into kwangsu61-master
Adding test for #457
0.9.1
Updating changelog.md for 0.9.1