Revert "Replace on_load with instance_eval"

This reverts commit 04dfaf74eecca0745efa3e45636d76524380d6f6.

reason: Killing the lazy-load hook obviously causes performance regressions in some cases
Make sure that AV::Base is activated before running the Rake tasks
Merge pull request #116 from amatsuda/lazy_load_action_view

Bring back action_view lazy loading