Add docker files for local testing.

* Use docker to locally run tests on multiple perl versions
    * perlbrew used to install multiple perls
    * perl environments bootstrapped when image built
* Based on travis configuration
* Adds docker folder to MANIFEST.SKIP
* Running image runs all tests.
    * If exit with no error, then all tests pass.
* ./build-docker.sh builds stow testing image.
* ./test-docker.sh runs stow testing image.
    * Assumes built with options in build-docker.sh
* *-docker.sh scripts added to MANIFEST.SKIP

docker/Dockerfile

@@ -0,0 +1,47 @@
+# Build docker image: `docker build -t stowtest`
+# Run tests: (from stow src directory) 
+#    `docker run --rm -it -v $(pwd):$(pwd) -w $(pwd) stowtest`
+FROM debian:jessie
+RUN DEBIAN_FRONTEND=noninteractive \
+apt-get clean && \
+apt-get update -qq && \
+apt-get install -y -q \
+    autoconf \
+    bzip2 \
+    cpanminus \
+    gawk \
+    git \
+	libssl-dev \
+    make \
+	patch \
+    perlbrew \
+    texinfo \
+    texlive \
+    texi2html \
+&& rm -rf /var/lib/apt/lists/*
+
+# Set up perlbrew
+ENV HOME=/root \
+    PERLBREW_ROOT=/usr/local/perlbrew \
+    PERLBREW_HOME=/root/.perlbrew \
+    PERLBREW_PATH=/usr/local/perlbrew/bin
+RUN mkdir -p /usr/local/perlbrew /root \
+    && perlbrew init \
+	&& perlbrew install-cpanm \
+	&& perlbrew install-patchperl \
+    && perlbrew install-multiple -j 4 --notest \
+        perl-5.22.2 \
+        perl-5.20.3 \
+        perl-5.18.4 \
+        perl-5.16.3 \
+        perl-5.14.4 \
+&& perlbrew clean
+
+# Bootstrap the perl environments
+COPY ./bootstrap-perls.sh /bootstrap-perls.sh
+RUN /bootstrap-perls.sh && rm /bootstrap-perls.sh
+
+# Add test script to container filesystem
+COPY ./run-stow-tests.sh /run-stow-tests.sh
+
+ENTRYPOINT ["/run-stow-tests.sh"]