Docs: deploy.rst is very out of date

### What was wrong?
I tried following the docs for deployment [here](http://populus.readthedocs.io/en/latest/deploy.html#id3) and in particular I get an error for trying to use the `get_contract_factory()` method of the `Chain` class:

```python
Token = chain.get_contract_factory('Token')
AttributeError: 'TestnetChain' object has no attribute 'get_contract_factory'
```

I'm trying to find the right method to use from trawling the code, but in the mean time let this serve as a placeholder that the deployment doc is very out of date

Start with the deployment documentation at deploy.rst and compare its get_contract_factory() example with the current Chain API in the code. Identify the supported deployment method, update the outdated instructions, and verify that the documented example no longer raises the reported AttributeError.

Written by the indexing model from the issue text.