Continue improving documentation and examples.

* README.md
  (Overview): Rephrase to clarify.
  (Administrating E-Vote): Clarify how to set initial password.
  (Customizing E-Vote's Appearance): Expand.
  (Registering Users and Running Elections): New section.
  (Concluding Elections): New section.
  (Testing E-Vote Without Email): New section.

* models/messages.py
  (db.election.ballot_model.default): Make more self-explanatory.
Merge branch 'master' of github.com:mdipierro/evote