Add support for project.el

[doolio]

Perhaps an elpy-project-find-project-root? Also, is this defcustom missing an elpy-project-find-django-root option at the very least?

(defcustom elpy-project-root-finder-functions
  '(elpy-project-find-projectile-root
    elpy-project-find-python-root
    elpy-project-find-git-root
    elpy-project-find-hg-root
    elpy-project-find-svn-root)
  "List of functions to ask for the current project root.
These will be checked in turn. The first directory found is used."
  :type '(set (const :tag "Projectile project root"
                     elpy-project-find-projectile-root)
              (const :tag "Python project (setup.py, setup.cfg)"
                     elpy-project-find-python-root)
              (const :tag "Git repository root (.git)"
                     elpy-project-find-git-root)
              (const :tag "Mercurial project root (.hg)"
                     elpy-project-find-hg-root)
              (const :tag "Subversion project root (.svn)"
                     elpy-project-find-svn-root)
              (const :tag "Django project root (manage.py, django-admin.py)"
                     elpy-project-find-django-root))
  :group 'elpy)