Remove apt caches and lists after successfull installation.

This reduces the image size for about 8 megabytes.

Author: thresheek

Dockerfile

@@ -7,7 +7,7 @@ RUN echo "deb http://nginx.org/packages/mainline/debian/ wheezy nginx" >> /etc/a
 
 ENV NGINX_VERSION 1.7.7-1~wheezy
 
-RUN apt-get update && apt-get install -y nginx=${NGINX_VERSION}
+RUN apt-get update && apt-get install -y nginx=${NGINX_VERSION} && apt-get clean && rm -rf /var/lib/apt/lists/*
 
 # forward request and error logs to docker log collector
 RUN ln -sf /dev/stdout /var/log/nginx/access.log