Refactor.

 - Attempt to streamline the package, cutting out unnecessary structures such as
   the 'Observatory' class, when we can do without.
 - Cut down on inter-module dependencies.
 - Use of templates for email formatting should be much easier to read and
   maintain.
 - Remove 'address_book.py' module, instead import contacts from a JSON file
   in the user's home area (``~/.pysovo/contacts.json``).