Add Debian Jessie build image

This image is meant to be used to build packages for the Jessie release of Debian. See debian/nginx-build.

debian/jessie/Dockerfile

@@ -27,7 +27,6 @@ RUN apt-get update \
         libpcre3 \
         libpcre3-dev \
         libz-dev \
-        shellcheck \
         gnupg \
         libssl-dev \
     && apt-get clean \