TODO
- TT driver should die with Template->error if $driver = Template->new(\%config) fails

- [under debate] allow native syntax for include paths to also work in
  addition to the include_paths param

- improve handling of config params (avoid copious copying of hashes)
- possibly remove dependency on Clone

- emulate creating template from string in Petal
  (or possibly support Template::TAL)

- CPAN installer that lets you pick your template driver(s)
- find out how to make subclassing of CAP::AT possible