Data type check on redis array host info

RedisArray will segfault if you pass something other than strings
into your array of hosts.  This is invalid input (needs strings here)
but it shouldn't crash php.
Merge branch 'hotfix/ra_type_check'
Fix autorehashing in RedisArray

This commit fixes auto rehashing in RedisArray as well as fixes
a couple of memory leaks found along the way

Addresses #442 and #294
Merge branch 'hotfix/ra_autorehash'