Update dockerfile

Dockerfile

@@ -1,13 +1,17 @@
-FROM alpine:3.5
+FROM python:2-alpine
 
 ENV WEB_CONCURRENCY=4
 
 ADD . /httpbin
 
-RUN apk add --update python python-dev py-pip build-base ca-certificates libffi-dev
-RUN pip install --upgrade pip
-RUN pip install gunicorn && pip install /httpbin
+RUN apk add -U ca-certificates libffi libstdc++ && \
+    apk add --virtual build-deps build-base libffi-dev && \
+    # Pip
+    pip install --no-cache-dir gunicorn /httpbin && \
+    # Cleaning up
+    apk del build-deps && \
+    rm -rf /var/cache/apk/*
 
 EXPOSE 8080
 
-CMD gunicorn -b 0.0.0.0:8080 httpbin:app
+CMD ["gunicorn", "-b", "0.0.0.0:8080", "httpbin:app"]