We deprecated controller and view specs on the grounds that they were
brittle, and were a poorer measure of user experience than feature
specs. However, feature specs have their own problems: they're much
slower to run, and flakier (see #901). We also ran into a few cases
where feature specs erroneously passed because they were checking for
the presence of a string that occurred in the error page!
Hence, we're cautiously un-deprecating controller and view specs.
Fixes#1132
