Upgrade Appraisals to 1.0.0

- remove gemfiles directory from the tree (there is no point of keeping pre-generated files
inside the git) and add it to gitignore,
- update AR and AS to the latest for each branch,
- remove appraisals from the rake file as it is not needed anymore,

Instruction how to use new Appraisals

 # generate gemfiles
 > appraisals install

 # run tests for specific gemfile
 > appraisals rails2 rake test