Improve getting started documentation

On Fedora 19, I was getting this error following the documentation as written,
which did not mention bundle dependencies.

    Your Ruby version is 2.0.0, but your Gemfile specified 1.9.3

The small change to fix this is to disable the ruby line in the Gemfile.

In addition, this patch adds more explicit documentation on system level
dependencies and project level dependencies.
Fix rake not working with bundler

Without this patch I'm getting the following error.  This patch addresses the
problem by specifying rake as a project dependency.

    /usr/bin/rake:35:in `require': cannot load such file -- rake (LoadError)
        from /usr/bin/rake:35:in `<main>'
Fix thor not working with bundler

Without this patch I'm getting the following error running `bundle exec rake
build`

    rake aborted!
    cannot load such file -- thor
    /work/razor-el-mk/Rakefile:1:in `require'
    /work/razor-el-mk/Rakefile:1:in `<top (required)>'
    (See full trace by running task with --trace)

This patch addresses the problem by specifying `thor` as a dependency in the
Gemfile.