Switch to pipenv

[kylef]

I wanted to update some of the dependencies as GitHub mentions there are potential security problems with some versions are we are using:

It's a little tricky to manage the versions with requirements.txt locking so I though we'd move to Pipenv as we have in other places, pipenv support in readthedocs is coming soon (readthedocs/readthedocs.org#4783). I've managed to retain compatibility by creating a requirements.txt file from the Pipfile.lock (pipenv lock -r --dev > requirements.txt). Once pipenv support is available in RTD we can remove the requirements.txt and add a a configuration for pipfile:

diff --git a/.readthedocs.yml b/.readthedocs.yml
new file mode 100644
index 0000000..c112522
--- /dev/null
+++ b/.readthedocs.yml
@@ -0,0 +1,7 @@
+version: 2
+sphinx:
+  configuration: docs/conf.py
+python:
+  install:
+    - pipfile: .
+      dev: true

[honzajavorek]

pipenv lock -r --dev > requirements.txt

I've been using https://github.com/gsemet/pipenv-to-requirements 😮