Evaluation and Reduction with environment should use a Map instead of a List to represent the Environment

```
This is another breaking change in this part of the API, but in the long run is 
the right choice and being a new feature as of version 2.0.0 we can consider 
these "experimental" parts of the API.

This does not affect the unit testing Assertion API.

```

Original issue reported on code.google.com by `stephen....@gmail.com` on 13 Jul 2011 at 11:12
