Added a setup.py file for Python's pip

Also added a setup.cfg template to specify paths to the libraries we need (mainly useful on Windows where CMake needs the locations).
Updated .gitignore.

On Windows, it uses the "Visual Studio 14 2015 Win64" generator.

.gitignore

-# Ignore the user-specific initial_cache file
+# Ignore (optional) configuration files with user-specific paths:
 initial_cache.cmake
+setup.cfg

setup.cfg.template

+# This file goes with setup.py and is the (optional) config file for generating
+# pip and wheel packages for eos's Python bindings.
+# Rename to setup.cfg to use.
+[build_ext]
+# Uncomment and set these paths if required (usually on Windows):
+#boost-root=C:/boost_1_59_0
+#eigen3-include-dir=C:/eigen-3.3.2
+#opencv-dir=C:/opencv/install

setup.py

+import os
+import re
+import sys
+import platform
+import subprocess
+
+from setuptools import setup, Extension
+from setuptools.command.build_ext import build_ext
+from distutils.version import LooseVersion
+
+
+class CMakeExtension(Extension):
+    def __init__(self, name, sourcedir=''):
+        Extension.__init__(self, name, sources=[])
+        self.sourcedir = os.path.abspath(sourcedir)
+
+
+class CMakeBuild(build_ext):
+
+    # user_options are best specified in setup.cfg, this works for both pip and 'python setup.py'.
+    # Via command-line, it might be possible like this:
+    #     setup.py: $ python setup.py --help build_ext
+    #     For pip, it might be something like that but it doesn't work:
+    #         $ pip install .\eos --build-option="--opencv-dir=C:/opencv/install"
+    # So just use setup.cfg instead.
+    # -----
+    # The second argument is an optional short option (can e.g. be 'b').
+    # It seems options need to be lower-case.
+    user_options = build_ext.user_options + [
+        ('boost-root', None, "Boost search location"),
+        ('eigen3-include-dir', None, "Directory of the Eigen3 headers"),
+        ('opencv-dir', None, "OpenCV config dir, where OpenCVConfig.cmake can be found")
+    ]
+
+    def initialize_options(self):
+        build_ext.initialize_options(self)
+        self.boost_root = None
+        self.eigen3_include_dir = None
+        self.opencv_dir = None
+
+    def run(self):
+        try:
+            out = subprocess.check_output(['cmake', '--version'])
+        except OSError:
+            raise RuntimeError("CMake must be installed to build the following extensions: " +
+                               ", ".join(e.name for e in self.extensions))
+
+        if platform.system() == "Windows":
+            cmake_version = LooseVersion(re.search(r'version\s*([\d.]+)', out.decode()).group(1))
+            if cmake_version < '3.1.0':
+                raise RuntimeError("CMake >= 3.1.0 is required on Windows")
+
+        for ext in self.extensions:
+            self.build_extension(ext)
+
+    def build_extension(self, ext):
+        extdir = os.path.abspath(os.path.dirname(self.get_ext_fullpath(ext.name)))
+        cmake_args = ['-DCMAKE_LIBRARY_OUTPUT_DIRECTORY=' + extdir,
+                      '-DPYTHON_EXECUTABLE=' + sys.executable,
+                      '-DEOS_BUILD_EXAMPLES=OFF',
+                      '-DEOS_GENERATE_PYTHON_BINDINGS=ON'
+                      ]
+        if self.opencv_dir:
+            cmake_args += ['-DOpenCV_DIR:PATH=' + self.opencv_dir]
+        if self.boost_root:
+            cmake_args += ['-DBOOST_ROOT:PATH=' + self.boost_root]
+        if self.eigen3_include_dir:
+            cmake_args += ['-DEIGEN3_INCLUDE_DIR:PATH=' + self.eigen3_include_dir]
+
+        cfg = 'Debug' if self.debug else 'Release'
+        build_args = ['--config', cfg]
+
+        if platform.system() == "Windows":
+            cmake_args += ['-G', 'Visual Studio 14 2015 Win64']
+            cmake_args += ['-DCMAKE_LIBRARY_OUTPUT_DIRECTORY_{}={}'.format(cfg.upper(), extdir)]
+            build_args += ['--', '/m']
+        else:
+            cmake_args += ['-DCMAKE_BUILD_TYPE=' + cfg]
+            build_args += ['--', '-j2']
+
+        env = os.environ.copy()
+        env['CXXFLAGS'] = '{} -DVERSION_INFO=\\"{}\\"'.format(env.get('CXXFLAGS', ''),
+                                                              self.distribution.get_version())
+        if not os.path.exists(self.build_temp):
+            os.makedirs(self.build_temp)
+        subprocess.check_call(['cmake', ext.sourcedir] + cmake_args, cwd=self.build_temp, env=env)
+        subprocess.check_call(['cmake', '--build', '.'] + build_args, cwd=self.build_temp)
+
+setup(
+    name='eos',
+    version='0.11.0',
+    author='Patrik Huber',
+    author_email='patrikhuber@gmail.com',
+    description='Python bindings for eos - A lightweight 3D Morphable Face Model fitting library in modern C++11/14',
+    long_description='',
+    url='https://github.com/patrikhuber/eos',
+    license='Apache-2.0',
+    ext_modules=[CMakeExtension('eos')],
+    cmdclass=dict(build_ext=CMakeBuild),
+    zip_safe=False,
+)