Add a spec_helper to run specs against live redis

You can invoke it by running

    bundle exec rspec -r spec_helper_live_redis.rb spec

And it'll connect to a redis instance running on localhost:6379/0, and run the test suite against it. Making sure that the specs are accurate against a live redis instance running redis-rb 3.0.0 (at the time of committing). This is so we can be sure that our specs are accurate compared to what live redis would return, so we can have an accurate fake-redis mocking out live redis.
Fix specs to work against live redis

Using redis-rb v2.2.2 against redis 2.6.7
raise RuntimeError instead of ArgumentError

Matches exactly what redis-rb raises.
Fix zinterstore's behaviour when given an unsorted set
Make lrange return an array if nothing matches
Pull in our rspec helpers in our own rspec suite
Fix issue with incr/decr incrby/decrby command handling of TTLs
Discarding from a set with and offset that is larger than the set, should not fail
Correctly support lpush/rpush variadic commands

With redis-rb v2.2.2 this means we don't actually support them. The second argument has #to_s called and that added as a single value.
Update fakeredis.gemspec

* Add MIT license
* Update homepage
* Remove rubyforge project
Check data type in `get` accessing keys

Also raises a Redis::CommandError for wrong key value types, to match the redis-rb gem's behaviour.
Type check & delegate to #set from #getset

`getset` only operates against string values, so the key needs to be checked to hold a string. And it should also convert the value set to a string, so it just delegates to `set` in the implementation for that now.
Move out subclasses into their own files
Check responses from #flushall/#flushdb/#select

Conflicts:
	spec/server_spec.rb
Add documentation about old versions of redis-rb
Update Acknowledgements
Update Acknowledgements
Some specs for more accurate redis-rb behaviour

Verified the entire suite still passes with redis-rb v2.2.2 using `bundle exec rspec -r spec_helper_live_redis.rb spec`.
Make the lists spec pass

Conflicts:
	lib/redis/connection/memory.rb
Handle non-existent methods

Also use `meffod` for variable name, as `method` is a method in ruby already. Object#method - http://ruby-doc.org/core-1.9.3/Object.html#method-i-method