Optimize docker image

Dockerfile

@@ -1,16 +1,48 @@
-FROM alpine:3.5
+FROM python:3-alpine
 
-RUN apk add --update-cache py3-pip ca-certificates py3-certifi py3-lxml\
-                           python3-dev cython cython-dev libusb-dev build-base \
-                           eudev-dev linux-headers libffi-dev openssl-dev \
-                           jpeg-dev zlib-dev freetype-dev lcms2-dev openjpeg-dev \
-                           tiff-dev tk-dev tcl-dev
+ENV REQUESTS_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt
 
 COPY setup.py README.rst requirements.txt /build/
-RUN pip3 install -r /build/requirements.txt
-
 COPY aws_google_auth /build/aws_google_auth
-RUN pip3 install -e /build/[u2f]
 
-ENV REQUESTS_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt
+RUN apk add --update --no-cache \
+        ca-certificates \
+        libxml2 \
+        libxslt \
+        eudev-libs \
+        libffi \
+        openssl \
+        jpeg \
+        zlib \
+        freetype \
+        lcms2 \
+        openjpeg \
+        libusb \
+        tiff \
+        tk \
+        tcl && \
+    apk add --update --no-cache --virtual .builddeps \
+        build-base \
+        cython-dev \
+        libxml2-dev \
+        libxslt-dev \
+        eudev-dev \
+        libffi-dev \
+        openssl-dev \
+        jpeg-dev \
+        zlib-dev \
+        freetype-dev \
+        lcms2-dev \
+        openjpeg-dev \
+        libusb-dev \
+        tiff-dev \
+        tk-dev \
+        tcl-dev && \
+    rm -rf /var/lib/apt/lists/* && \
+    rm -rf /var/cache/apk/* && \
+    pip install -Ur /build/requirements.txt && \
+    pip install -Ue /build/[u2f] && \
+    apk del .builddeps && \
+    rm -rf .builddeps
+
 ENTRYPOINT ["aws-google-auth"]