Clean up README files to be more clear and helpful

Howdy!

Great gem, but boy was it frustrating to figure out how to use it. The sub-readme files are confusing, and some of the documentation is just out of date.

This set of changes cleans things up. I've removed links to https://github.com/jodosha/redis-store/wiki/Frameworks-Configuration, which I recommend be removed. It is out of date and confusing. Everything it covers should be covered in the readmes now.

* Move build status to the top of the main readme.
* Move to two-space tabs, like most of the Rails community.
* Drop redis installation instructions from every readme.
* Correct the build instructions. Install before exec.
* Refer users to redis-rails from the individual gems.
* Update the redis-rails readme to be more up-to-date.
* Use Ruby 1.9 conventions for code samples.