pass the app to getModel when constructing a model from the options passed to a view
throw an Error if options.app is not specified
Revert "throw an Error if options.app is not specified"

This reverts commit 3c7cfec404e4f123d3c0d19f0b10761c58baef90.
Merge pull request #405 from change/md_pass_app_to_getmodel

pass the app to getModel when constructing a model from the options passed to a view