[vim] Move unite keybindings to the correct file.

The core vimrc files should not contain any plugin mappings, as they
should not be included in the minimal vimrc file.
[vim] Move goyo binding from 03-input to a different file
[vim] Move file finder plugin config to a separate file.
[vim] Move 'kill on save' commands to a separate file.

This way, these auto commands are not included in the minimal vimrc.
[vim] Update vim readme
[vim] Add restructured text config