chore: remove mentions of pycrypto (#799)

diff --git a/README.md b/README.md
index 30410b8..a039ec6 100644
--- a/README.md
+++ b/README.md
@@ -58,7 +58,6 @@
 
 For development you will also need the following libraries:
 * [WebTest](http://webtest.pythonpaste.org/en/latest/index.html)
-* [pycrypto](https://pypi.python.org/pypi/pycrypto)
 * [pyopenssl](https://pypi.python.org/pypi/pyOpenSSL)
 
 ## Contributing
diff --git a/tox.ini b/tox.ini
index 13a718b..1d9bc13 100644
--- a/tox.ini
+++ b/tox.ini
@@ -11,7 +11,6 @@
        google-auth-httplib2
        mox
        pyopenssl
-       pycrypto==2.6
        django<2.0.0; python_version < '3.0.0'
        django>=2.0.0; python_version > '3.0.0'
        flake8