[INCOMPATIBLE CHANGES]
- Gives you warnings when you use one of Plack::App objects in `plackup -e` or
in .psgi files but forgot to call ->to_app to make it a PSGI application (#369)
Still automatically converts them for backward compatibility, but in the
loading time inside Plack::Builder.
[BUG FIXES]
- chdir to the CGI path when executing CGIBin (#338, #368)