Feature/fix swagger

Fixes #10

- all `Duration` types are now `Duration` in the models since nothing opposes it
- manual annotation of most fields in models (still wasting less time than contributing to swagger)
- raised issues https://github.com/wordnik/swagger-core/issues/673 and https://github.com/wordnik/swagger-codegen/issues/258 , without much hope
- upgraded to latest Swagger snapshot (1.3.9-SNAPSHOT)
Tests for this new module please (just the new duration serialisation/deserialisation functionality is fine).