install mapnik-sdk and run demo

[hcfang2000]

I think I have had a successful build following the build procedures. I get a full mapnik-sdk sub-directory and it looks like it's the build result.

What's the right way to install it? I could not find any documentation or instructions for the following steps. I could not run the demo rundemo.py successfully either under the new build.

[wilhelmberg]

I could not run the demo rundemo.py successfully either under the new build.

It's not possible to run the Python bindings/demos as they are currently failing to build on Windows, see #92

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Quick rundown for the C++ demo:

CD into mapnik SDK directory
set-env-vars.bat
cd demo\c++
git clone https://chromium.googlesource.com/external/gyp.git gyp
gyp\gyp.bat rundemo.gyp --depth=. -f msvs -G msvs_version=2015
rundemo.sln <- this opes VS

Add x64 platform to the solution
Change the following paths in rundemo.cpp:

• register_datasources => lib/mapnik/input/
• register_font => lib/mapnik/fonts/dejavu-fonts-ttf-2.37/ttf/DejaVuSans.ttf

Build and exit VS.

cd back into the root directory of the mapnik SDK
demo\c++\Debug\rundemo.exe

You should now have some demo.* in the root directory of mapnik SDK.

[hcfang2000]

Your step-by-step instruction is really INVALUABLE. It works. Too happy!

This instructions should be put inside the README.md. Thank you very very much.