Added states script to convert long state names to abbreviations.

In order to push this to production (of course testing on staging first), we need to start `python manage.py shell` and execute:
```python
import states
fix_states()
```
Doing so grabs all contacts whose states are not in abbreviated form and replaces them with said abbreviations. 

The other changes are to reduce the maxlength of the state column to two characters, which has the effect of preventing the user from ever entering more than two characters in a form. I'd have opted for a state dropdown, but that would have required me to:
* change the mypartners.Contact model
* write a manage command to populate the states table
* create migrations for all the state columns that need to be changed
* write a script to migrate current data over

Might make for a good sprint item in the future once we decide to revisint user interaction. If we want this in the legacy master branch, the changes should be easy enough to cherry pick. Specifically, #39880ee
is relevant.