Remove transforms related option from build doc

Originally, I had planned to copy both sections and transforms to each
new project. However, if someone is interested in going deep enough to
make custom transforms, rather than just pick and choose pre-made
transforms with the config file, then they can just go ahead and add the
transforms to the source. I think having a transforms directory get
copied all over the place will just make it more confusing and make it
harder for people to upgrade.