Revert "Changed seneca dependency to 0.5.18 since it is now on github"

This reverts commit 01bacbdfa9395bd1d6d56120c3e279c127d19ee5.
Revert "Added link to senecajs.org/data-entities.html"

This reverts commit d8bdaec5a811828b7f43ec0fd2cea456016b02b3.
Revert "Updated example dependencies"

This reverts commit e3dd9df13ad50ce9fb0e2febeb64a051245f876b.