Align instructions in readme.txt and text on onehippo.org

The readme.txt has different instructions as http://www.onehippo.org/library/essentials/using-essentials.html

e.g.

http://www.onehippo.org/trails/essentials-trail/building-a-project.html

or http://www.onehippo.org/trails/essentials-trail/running-a-project

especially "mvn -Pcargo.run -Drepo.path=storage -Drepo.bootstrap=true"

Consider removing instructions from readme.txt and refer to site to have a single source of truth.