Enable gitlab CI

Even though the overviewer repo is hosted on github, this new CI stuff
is useful for mirrors of overviewer hosted on gitlab.

To support package builds for a few distributions, a set of dockerfiles
have been created.

build-tools/dockerfiles/centos7/Dockerfile

@@ -0,0 +1,5 @@
+FROM code.em32.net:14567/overviewer/minecraft-overviewer:base
+RUN yum -y install mock
+RUN useradd --create-home --groups mock overviewer
+USER overviewer
+

build-tools/dockerfiles/centos7/Makefile

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+tag=centos7
+
+build:
+	docker build -t code.em32.net:14567/overviewer/minecraft-overviewer:$(tag) . 
+
+push:
+	docker push code.em32.net:14567/overviewer/minecraft-overviewer:$(tag)
+
+run:
+	docker run --rm --privileged -it code.em32.net:14567/overviewer/minecraft-overviewer:$(tag) /bin/bash
+

build-tools/dockerfiles/centos7/Minecraft-Overviewer.spec

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+Summary: Generates large resolution images of a Minecraft map.
+Name: Minecraft-Overviewer
+Version: {VERSION}
+Release: 1%{?dist}
+Source0: %{name}-%{version}.tar.gz
+License: GNU General Public License v3
+Group: Development/Libraries
+BuildRoot: %{_tmppath}/%{name}-%{version}-%{release}-buildroot
+Vendor: Andrew Brown <brownan@gmail.com>
+Url: http://overviewer.org/
+Requires: python-imaging, numpy
+BuildRequires: python-devel, python-imaging-devel, numpy
+
+%description
+The Minecraft Overviewer is a command-line tool for rendering high-resolution
+maps of Minecraft worlds. It generates a set of static html and image files and
+uses the Google Maps API to display a nice interactive map.
+
+%prep
+%setup -n %{name}
+
+%build
+env CFLAGS="$RPM_OPT_FLAGS" %{__python} setup.py build
+
+%install
+%{__python} setup.py install -O1 --root=%{buildroot}
+rm -rf %{buildroot}%{_defaultdocdir}/minecraft-overviewer
+
+%clean
+rm -rf %{buildroot}
+
+%files
+%defattr(-,root,root)
+%{python_sitearch}/Minecraft_Overviewer-*-*.egg-info
+%{python_sitearch}/overviewer_core
+%{_bindir}/overviewer.py
+%doc README.rst COPYING.txt sample_config.py