Test with Django 2.1 and Python 3.7 (#176)

* Test with Django 2.1 and Python 3.7
* Fix lint errors
* Remove setuptools-scm hack
* Factor out coverage script
* Cache .tox in travis
* Update README & docs

requirements/dev.txt

@@ -1,6 +1,4 @@
-# requirements for local development to be installed via pip install -r requirements/dev.txt
+# requirements for local development to be installed via pip install -U -r requirements/dev.txt
 -r tox.txt
 -r test.txt
 -r lint.txt
-
-tox-battery>=0.5

requirements/docs.txt

@@ -4,5 +4,5 @@ sphinx_rtd_theme>=0.2.4
 Pillow>=4.3.0
 readme_renderer>=17.2
 
-Django>=2.0,<2.1
+Django>=2.0
 djangorestframework_camel_case>=0.2.0

requirements/setup.txt

@@ -1,4 +1,3 @@
 # needed to build the package setup_requires in setup.py
 
-# do not unpin this (see setup.py)
-setuptools_scm==1.15.6
+setuptools-scm>=3.0.6

requirements/test.txt

@@ -1,5 +1,5 @@
 # requirements for running the tests via pytest
-pytest>=2.9
+pytest>=2.9,<3.7  # <3.7 because of incompatible pluggy requirement
 pytest-pythonpath>=0.7.1
 pytest-cov>=2.5.1
 pytest-xdist>=1.22.0

requirements/tox.txt

@@ -1,5 +1,5 @@
 # requirements for building and running tox
-tox>=2.9.1,<3.0.0
-detox>=0.11
+tox>=3.1.2
+tox-battery>=0.5
 
 -r setup.txt