Initial spike for Redic.
Make ohm work with redic edge.

Since redic now simply accepts a URL as opposed to a
hash of options, that causes some breakages with
the existing test suite.

This commit fixes all of the breakages.
Include EINVAL in the possible errors.
Remove connection magic of Ohm.

This change, spawned by @djanowski, relies on the redis
client, in this case Redic, to be thread safe.

Instead of having a #connect method, we simply store
a `@redis` class variable in Ohm, and all models
inherits from that by default.

For cases where certain models need to connect to different
databases, they simple have to override that, i.e.

    User.redis = Redic.new(ENV["REDIS_URL2"])
Centralize Lua logic into a module.

This is similar to the first iteration we did a year ago,
but cheats a bit by pre-caching the SHA1s of each individual
lua file.

In addition, we use SCRIPT EXISTS - SCRIPT LOAD mechanics
as opposed to an EVAL FAIL EVALSHA1 method.

SCRIPT EXISTS results are memoized in-ruby (on a per
redis instance - lua file pair) to avoid unnecessary
repeated lookups.
Write a basic rake task to print sha1s.
Add script function for sending lua commands.
Merge branch 'redic' of github.com:soveran/ohm into redic

Conflicts:
	lib/ohm.rb
Remove Lua module.
Capture RuntimeError.