Rewrite schema generation (#1)

* Completeley rewritten schema generation
* Added support for python 2.7 and 3.4
* Restructured testing and build configuration
* Added nested request schemas

This rewrite completely replaces the public interface of the django rest schema generation library, so 
further changes will be needed to re-enable and further extend the customization points one might want.

requirements/base.txt

@@ -0,0 +1,6 @@
+coreapi>=2.3.3
+coreschema>=0.0.4
+openapi_codec>=1.3.2
+ruamel.yaml>=0.15.34
+inflection>=0.3.1
+future>=0.16.0

requirements/ci.txt

@@ -0,0 +1,4 @@
+# requirements for CI test suite
+-r dev.txt
+tox-travis>=0.10
+codecov>=2.0.9

requirements/dev.txt

@@ -0,0 +1,3 @@
+# requirements for local development
+tox>=2.9.1
+tox-battery>=0.5

requirements/test.txt

@@ -0,0 +1,11 @@
+# pytest runner + plugins
+pytest-django>=3.1.2
+pytest-pythonpath>=0.7.1
+pytest-cov>=2.5.1
+
+# test project requirements
+Pillow>=4.3.0
+pygments>=2.2.0
+django-cors-headers>=2.1.0
+django-filter>=1.1.0,<2.0; python_version == "2.7"
+django-filter>=1.1.0; python_version >= "3.4"

requirements/validation.txt

@@ -0,0 +1,3 @@
+# requirements for the validation feature
+flex>=6.11.1
+swagger-spec-validator>=2.1.0