Initial commit of eselect type/provider

It reads the equivalent fact in order to get the current state
Usage examples:

eselect { 'ruby':
  set => 'ruby19',
}

(In case of eselect sub-modules):

eselect { 'php_apache2':
  set => 'php5.3',
}

fixes #29
Merge pull request #54 from tampakrap/eselect

Initial commit of eselect type/provider
Add info about eselect in the README
Merge pull request #57 from tampakrap/readme

Add info about eselect in the README
Merge remote-tracking branch 'origin/2.x'