Redesign Cob Spec to be easier to use.

This is a major redesign to how cob spec works.
- Updated fitnesse to the latest version.
- Combined tests into a single suite.
- Removed duplication in fixture code.
- Updated tests to new fixture code.
- Updated .rvmrc to 1.9.3
- Removed Rubyslim submodule because it did not work with 1.9.3.
- Updated README with new instructions.

There are probably some other minor changes that I've forgotten.
Update README and and Gemfile

Updated the readme to be clearer. Updated gemfile to add missing
gems and updated gem versions. Modified server fixture to allow
different kinds of servers to be started. Fixed table formatting
in tests.
Merge pull request #13 from marosluuce/master

Redesign to make Cob Spec easier to use.