standardize code

Contributor Works
- [x] convert code to PSR-0
- [x] travis.yml
- [x] composer.json
- [x] init phpunit (Document::parse for now)
- [ ] migrate tests from the python repository
- [ ] add missing phpdocs

Prismic Works
- [ ] review works 
- [ ] register the repository to travis
- [ ] register the repository to packagist.org with auto update