Explain what's in dotfiles

* Link to fork/upstream process.
* Remove RVM reference.
* Don't create ~/.README.md in `install.sh` script.
Fix contributors link in README
Rename current file in vim buffer

* Retain relative path.
* Save file.
* Do not keep old file open in buffer.

Usage:

    :e old_file_name.rb
    :Rename new_file_name.rb
Change the 'git commit --amend' alias to 'git ca'