pkg_upstream_url is required in core plans
When using `hab plan init` to create a new core plan, we will fail the
build in travis because we're enforcing that all packages have a
project home page - `pkg_upstream_url`:
@@ -41,6 +41,10 @@ pkg_shasum=TODO
# of your package.
# pkg_description="Some description."
+# Required for core plans, optional otherwise.
+# The project home page for the package.
+# pkg_upstream_url=http://example.com/project-name
+
# Optional.
# An array of valid software licenses that relate to this package.
# Please choose a license from http://spdx.org/licenses/
