Update Dockerfile.

- Install new packages needed to deploy search
- Optimize dockerfile for more docker deamon caching
- Pin a python2.7 base image.

Dockerfile

@@ -1,21 +1,22 @@
-FROM debian:stable
+FROM python:2.7-slim
 
-RUN apt-get update && \
-    apt-get install -y --no-install-recommends \
-            python-dev python2.7-minimal python-virtualenv \
-            python-pybabel python-pip zlib1g-dev \
-            libxml2-dev libxslt1-dev build-essential \
-            openssl
+WORKDIR /app
 
 RUN useradd searx
 
-WORKDIR /app
-RUN pip install uwsgi
+EXPOSE 5000
+CMD ["/usr/local/bin/uwsgi", "--uid", "searx", "--gid", "searx", "--http", ":5000", "-w",  "searx.webapp"]
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+            zlib1g-dev libxml2-dev libxslt1-dev libffi-dev build-essential \
+            libssl-dev openssl && \
+    rm -rf /var/lib/apt/lists/*
+
+RUN pip install --no-cache uwsgi
+
 COPY requirements.txt /app/requirements.txt
-RUN pip install -r requirements.txt
+RUN pip install --no-cache -r requirements.txt
 
 COPY . /app
 RUN sed -i -e "s/ultrasecretkey/`openssl rand -hex 16`/g" searx/settings.yml
-
-EXPOSE 5000
-CMD ["/usr/local/bin/uwsgi", "--uid", "searx", "--gid", "searx", "--http", ":5000", "-w",  "searx.webapp"]