Update the db_prep_ prototypes to work with Django 1.2+

Django 1.2 introduced multiple DB connections. And Django 1.4
removes the compatibility layer. Update our prototypes so we
work with Django 1.2+ or later.
Update version of py-moneyed required.

Actually the current development version is fine.
So that migration works, specify the default currency in text form.

It is already indicated later on but is easily missible.
Fix exception on empty default_manager Django >1.4

Some minor enhancements:

  - Setting CURRENCIES to set the default Currency list on the admin
  - Documentation about how to add a new Currency
Fix typos ~sigh
Use cls.objects when we check for objects attribute, fixes issue #6
Merge pull request #7 from dekkers/fix-issue-6

Fix issue #6
Merge pull request #5 from akumria/jakewins-master

Update the db_prep_ prototypes to work with Django 1.2+
Fix Attribute error when model inherit manager

AttributeError: 'NoneType' object has no attribute 'get_query_set'
When a Model inherit from an Abstract one which implement a Manager.
In this case '_default_manager' is defined but equal to None
Merge pull request #11 from rach/master

Fix AttributeError when Model inherit a mager
Updated readme, closes #1, a year later :)
Added dependency on py-moneyed to setup.py
Making Django 1.5 compatible

Since an internal refactoring in Django 1.5
LOOKUP_SEP is up one level.
Embarrasing type

Edit files online has its dangers
Merge reinbach fork
FIX Correct import
Don't override the original display_for_field

It works better and is missing changes on Django 1.5
Fix missing representation for value
fix unexpected keyword argument 'frozen_by_south'
add kwarg currency_choices to models.fields.MoneyField