Add make docs command for building docs

Signed-off-by: Ben Firshman <ben@firshman.co.uk>

Dockerfile-docs

+FROM python:2.7
+
+RUN mkdir /home/docker-py
+WORKDIR /home/docker-py
+
+COPY docs-requirements.txt /home/docker-py/docs-requirements.txt
+RUN pip install -r docs-requirements.txt
+
+COPY . /home/docker-py

Makefile

@@ -13,6 +13,9 @@ build:
 build-py3:
 	docker build -t docker-py3 -f Dockerfile-py3 .
 
+build-docs:
+	docker build -t docker-py-docs -f Dockerfile-docs .
+
 build-dind-certs:
 	docker build -t dpy-dind-certs -f tests/Dockerfile-dind-certs .
 
@@ -57,3 +60,6 @@ integration-dind-ssl: build-dind-certs build build-py3
 
 flake8: build
 	docker run docker-py flake8 docker tests
+
+docs: build-docs
+	docker run -v `pwd`/docs:/home/docker-py/docs/ -p 8000:8000 docker-py-docs mkdocs serve -a 0.0.0.0:8000

docs-requirements.txt

-mkdocs==0.9
+mkdocs==0.15.3