Merge pull request #34 from mottosso/master

Merging both mine and Toke's requests and moving on!
Merge pull request #38 from mottosso/master

Calling this good and moving on!
Merge pull request #42 from mottosso/master

Merging and documenting "domain.py" a little better in Wiki.
https://github.com/abstractfactory/publish/wiki/Quickstart#domainpy
- Implemented publish.main.validate_all() to perform validations without actually publishing.
- Moved domain functions to domain.py
- Updated test-suite with an additional scene for selection testing
- Updated abstract.py to reflect current interfaces