More info for undefined template error

Closes https://github.com/phoenixframework/phoenix/issues/266

This PR does the ff:
1. Adds test case for undefined template error
2. Include Module name of View in undefined template error

Wasn't sure where to put the test case. Was thinking either in `template_test` or in `view_test`. I put it in `view_test` since adding it in `template_test` led to a little more set-up(requiring files and aliases). Let me know if it was unnecessary to add the test case.
This is actually only applying the replace to the View modules within Phoenix's tests. Let's just remove it and interpolate __MODULE__