Added in small examples on how to show how to pass in context for preprocess variables.
Added in small examples on how to show how to pass in context for preprocess variables.

patlux/gulp-preprocess,jhtep/gulp-preprocess,patlux/gulp-preprocess,yesmeck/gulp-preprocess,terkill/gulp-preprocess,terkill/gulp-preprocess,activenode/gulp-preprocess,yesmeck/gulp-preprocess,jhtep/gulp-preprocess,arma-gast/gulp-preprocess,arma-gast/gulp-preprocess,activenode/gulp-preprocess