Add Leiningen

Author: jacebrowning

Dockerfile

@@ -2,4 +2,12 @@ FROM circleci/python:3.6.3-stretch-browsers
 
 # Pipenv
 
-RUN sudo pip install --upgrade pipenv && pipenv --version
+RUN sudo pip install --upgrade pipenv && \
+pipenv --version
+
+# Leiningen
+
+RUN sudo wget -q -O /usr/bin/lein \
+https://raw.githubusercontent.com/technomancy/leiningen/stable/bin/lein && \
+sudo chmod +x /usr/bin/lein && \
+lein --version