Install Pandoc per-user on Windows.
Disable WiX warning LGHT1076 ICE91.

It’s harmless. http://msdn.microsoft.com/en-us/library/aa369053(VS.85).aspx
WiX: remove unused reference to Desktop.
WiX: add product URL to the installation package metadata.
WiX: uninstall any previously installed version.
WiX: extract upgrade code into a define to avoid duplication.
Merge pull request #748 from sheremetyev/wix-peruser

Install Pandoc per-user on Windows