Almost revert c:bb890f3.
Because the 'prepare_app' method is invoked on load phase for an app.
So Devel::NYTProf is loaded too.
I expect that Devel::NYTProf does not load without 'enabled setting'.
added 'setup_env' for loading Devel::NYTProf with $ENV{NYTPROF}
fixed POD
Merge pull request #15 from bayashi/fix_nytprof_env

Fix nytprof env