Overall refactoring of codebase, increased test coverage.
**Backward incompatible**
- Development Status set to **4 - Beta**
- Models are specified as mixins so that registration to sqlalchemy orm works better. **This is a backward incompatible change** [d4d14e0](https://github.com/quantmind/pulsar-odm/commit/d4d14e04173fcd72a7401736b85d652f275cc599)
- Ability to retrieve a dialect for a model name. Fixes 8 [d418c01](https://github.com/quantmind/pulsar-odm/commit/d418c01ce6570823566868eef7cc5305de812c73)
Tests
- Test for create sql semantic. Fixes 9 [504b798](https://github.com/quantmind/pulsar-odm/commit/504b79826f7b022f4b4d1f37db1ffe3fc539952c)
- More test coverage [cbd31d6](https://github.com/quantmind/pulsar-odm/commit/cbd31d6f1abd141f300a5331c6ba81d74668652a)