prepare version 0.1

[amirkdv]

Having used the current organization of the cookbook, that is attributes names
and organization, and division of responsibilities between recipes, it seems
necessary to take a stab at making the cookbook easier to use and release 0.1
(also c.f #33):

• reorganize all the functionality that in one way or another
  populates the project directory (download, get from path, get from git repo)
  into three independent mutually exclusive recipes, one for each distinct way of
  populating the project root.
• make sure that a flat repo structure would work with
  node['get_project']['site_dir']='.'. Right now we are assuming a repo
  structure like the folowing, which does not have to be a requirement for using
  the cookbook:
  • <project_root>
    • <drupal_root>
      • index.php
      • includes
      • modules
      • sites
      • themes
      • ...
    • db
      • dump.sql.gz
    • scripts
      • post-install-script.sh
• Refactor README.md such that information about recipes and their roles is
  easy to access and short,
• Make generic instructions easier to find,
• Move away low level details from README.md to separate files, and merge
  those with the existing (stale) dev-notes.md.
• Provide versioning instructions (and compatibility cautions) in README.md,
• Release version 0.1