Fix segfault in phpiredis_command_bs() after attempted free of an uninitialized pointer and some potential memory leaks in the phpiredis_multi_command_*() functions. Fixes #20

The error occurred when the connection to the redis server was lost during a command. In that case the pointer to the reply object, which was uninitialized, would be freed, which leads to a segfault.
Merge remote-tracking branch 'theinz/fix-uninitialized-reply'