Internal structure changes

Merge pull request #19 from borenstein/debug

renamed "polytropos_demo" and "scenario" both to "example"

Improved internals and integration tests

Composites are now passed around as a wrapped Composite class, which has access both to the underlying data and the schema to which it (supposedly) conforms. Integration tests have been restored to the main codebase, rather than existing only in polytropos-demo.

Second releasee

Dependencies moved to setup.py
Deleted fixtures folder

First version

First version of the polytropos package