(doc) add building section to README
(doc) add building section to README

Provide some insight on the requirements that are not met simply by
running cake.

chocolatey/ChocolateyGUI,chocolatey/ChocolateyGUI,chocolatey/ChocolateyGUI,gep13/ChocolateyGUI,chocolatey/ChocolateyGUI,gep13/ChocolateyGUI,gep13/ChocolateyGUI,gep13/ChocolateyGUI,digital-carver/ChocolateyGUI,gep13/ChocolateyGUI,chocolatey/ChocolateyGUI