Raise ECONNRESET if socket#gets returns nil

Follows ruby driver approach. Fix for https://github.com/celluloid/celluloid-redis/issues/4
test for clean shutdown

Infrastructure for testing against a new redis instance.
guard against nil
get RedisInstance and latest test working well with jruby
Merge pull request #5 from simonrobson/read_should_raise_on_eof

Raise ECONNRESET if socket#gets returns nil