Graceful

New features:
- Bulk resource creation added (see 30)
- Support for optional contexts (see [design issue](https://github.com/swistakm/graceful/issues/32), 33)

Backwards-compatible API changes:
- All resource classes are by default _non-context-aware_.

Other changes:
- Documentation cleanup and reorganisation

**Notes:** Starting from `0.3.0` version the implicit declarations of _non-context-aware resource classes_ raise `FutureWarning`. Till `1.0.0` all resource classes should explicitly state if they are _context-aware_ or not using the `with_context` class definition keyword (similar to `metaclass` Python 3 keyword). After `1.0.0` graceful version release all resource classes will be _context-aware_ by default and implicit declaration will not raise any warnings. See [documentation on working with falcon context objects](http://graceful.readthedocs.io/en/latest/guide/working-with-resources.htmldealing-with-falcon-context-objects).

New features:
- `BoolParam` parameter class added (thanks to tomislater, 25)
- Parameter classes now support validation in same manner as field classes (see [param validation docs](http://graceful.readthedocs.io/en/latest/guide/parameters.htmlparameter-validation))
- Parameters with `many=True` option got support for custom containers (see [custom containers docs](http://graceful.readthedocs.io/en/latest/guide/parameters.htmlcustom-containers), 16)

Backwards compatible API changes:
- `req` and `resp` arguments for `describe()` method of resource classes are now optional to ease process of documentation generation (10)

Improvements:
- Massive docs overhaul
- New documentation section about how to construct API docs (14)
- `OPTIONS` request responses now include `Allow` header by default with the list of allowed HTTP methods (10),
- confirmed official support for falcon 1.0.0 and Python 3.5 (23)

Fixes:
- allow list resources to access uri template variables 21

Improvements:
- minor packaging improvements
- minor test cleanup and refactoring for the `graceful.resources.generic` module

Fixes:
- fix handling `application/json` content type handling if params in header provided

Features:
- allow multiple occurrences of the same parameter in query string (list)

Improvements:
- use shorter `super()` call and get rid of `object` inheritance

Fixes:
- type annotation of `StringField` changed from `'raw'` to `'string'`
- `ValidationError` now translates to `falcon.HTTPBadRequest` exceptions on resource level