j2labs/schematics — pull request #129 by lkraider (2013-06-05 19:44:18+00:00)
Title: Append model fields

This adds a method to append new fields to a model class.
Additionally, adds a copy method so that type instances can be copied.

Example:
```python
class Person(Model):
name = StringType()

Person.append_field('gender', Person.name.copy())
```