Add support to build docker-compose on ARM 32bit

Added a new Dockerfile (Dockerfile.armhf) specific for ARM 32 bit.
The Dockerfile was updated compare to default one:
  - Base image is armhf/debian instead of debian
  - Docker binary is downloaded with the correct arch (although it does not
    seems to be used)

Signed-off-by: Jean-Christophe Berthon <huygens@berthon.eu>

Dockerfile.armhf

@@ -0,0 +1,71 @@
+FROM armhf/debian:wheezy
+
+RUN set -ex; \
+    apt-get update -qq; \
+    apt-get install -y \
+        locales \
+        gcc \
+        make \
+        zlib1g \
+        zlib1g-dev \
+        libssl-dev \
+        git \
+        ca-certificates \
+        curl \
+        libsqlite3-dev \
+        libbz2-dev \
+    ; \
+    rm -rf /var/lib/apt/lists/*
+
+RUN curl https://get.docker.com/builds/Linux/armel/docker-1.8.3 \
+        -o /usr/local/bin/docker && \
+    chmod +x /usr/local/bin/docker
+
+# Build Python 2.7.13 from source
+RUN set -ex; \
+    curl -L https://www.python.org/ftp/python/2.7.13/Python-2.7.13.tgz | tar -xz; \
+    cd Python-2.7.13; \
+    ./configure --enable-shared; \
+    make; \
+    make install; \
+    cd ..; \
+    rm -rf /Python-2.7.13
+
+# Build python 3.4 from source
+RUN set -ex; \
+    curl -L https://www.python.org/ftp/python/3.4.6/Python-3.4.6.tgz | tar -xz; \
+    cd Python-3.4.6; \
+    ./configure --enable-shared; \
+    make; \
+    make install; \
+    cd ..; \
+    rm -rf /Python-3.4.6
+
+# Make libpython findable
+ENV LD_LIBRARY_PATH /usr/local/lib
+
+# Install pip
+RUN set -ex; \
+    curl -L https://bootstrap.pypa.io/get-pip.py | python
+
+# Python3 requires a valid locale
+RUN echo "en_US.UTF-8 UTF-8" > /etc/locale.gen && locale-gen
+ENV LANG en_US.UTF-8
+
+RUN useradd -d /home/user -m -s /bin/bash user
+WORKDIR /code/
+
+RUN pip install tox==2.1.1
+
+ADD requirements.txt /code/
+ADD requirements-dev.txt /code/
+ADD .pre-commit-config.yaml /code/
+ADD setup.py /code/
+ADD tox.ini /code/
+ADD compose /code/compose/
+RUN tox --notest
+
+ADD . /code/
+RUN chown -R user /code/
+
+ENTRYPOINT ["/code/.tox/py27/bin/docker-compose"]