Add Stretch

Now that Jessie works, let's build Stretch

debian/stretch/Dockerfile

+FROM debian:stretch
+
+LABEL maintainer="ethitter"
+LABEL version="1.0"
+
+RUN echo "deb http://security.debian.org/ stretch/updates main" >> /etc/apt/sources.list
+
+RUN apt-get update \
+    && apt-get -yqqf --no-install-recommends install \
+        apt-transport-https \
+        lsb-release \
+        ca-certificates \
+        curl \
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN curl -ssL -o /etc/apt/trusted.gpg.d/php.gpg https://packages.sury.org/php/apt.gpg
+RUN echo "deb https://packages.sury.org/php/ $(lsb_release -sc) main" > /etc/apt/sources.list.d/php.list
+
+RUN apt-get update \
+    && apt-get -y --no-install-recommends install \
+        git \
+        dh-make \
+        build-essential \
+        autoconf \
+        autotools-dev \
+        libpcre3 \
+        libpcre3-dev \
+        libz-dev \
+        gnupg \
+        libssl-dev \
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/*