Django-rest

* Fixed `open()` function in `setup.py` that broke on python 2.7.3 because of `encoding` keyword argument. The fix calls `io` native library that ensures backward compatibility for the `open()` built-in function.
* Removed useless `requirements.txt` that caused the dependency bot to raise security alerts (because of some known vulnerabilities on django 3.0.X)

The current version implements the whole CI pipeline using [Travis CI](https://travis-ci.org/). Here is what the pipeline does:
1. Checks code formatting using [black](https://github.com/psf/black)
2. Checks code validation using flake8
3. Runs unit-tests (with pytest)
4. Checks tests coverage using codecov

Also, more project details were displayed as badge in the project's main README file.

* Documented the whole project in the `README.md` file.
* Fixed bug that raised `ValueError` instead of `SerializationError` during serialization.
* Made `ValidationError` available from `django_rest.deserializers`.
* Improved `setup.py` and updated project's version.
* Added MIT license file to the project (`LICENSE.md`).
* Added `setup.cfg` file.

* Renamed `PerforatedDeserializer` into `AllPassDeserializer`.
* Refactored class-based decorated view for better performances.
* Fixed CSRF token bug for writing HTTP methods.
* Fixed Permission evaluation (made dynamic).

Main changes:
* Implementing the first `Deserializer`class
* Assuring support for all python's versions (2.7+, 3+), and django's versions (1.11+).
* Type hinting to improve code's readability.

Core `api_view` changes:
* Supporting `deserializer_class` parameter.
* Supporting deserializer class mapping (custom deserializers for each http method).
* Adding `allow_forms` parameter to accept forms data or raise error.
* Supporting for `api_view` syntax (only `api_view()` was supported before)
* Checking view's type to make sure it's either a function or a `django.views.View` class
* Normalizing requests payload between content_types, so that the output's always in the same format.
* Extracting query params and passing custom parameters for the view (query params, payload, url params, etc.).
* Decorating only class view's relevant methods (http methods) instead of all methods.
* Moving helpers function into separate file.