[html-formfu] Template::Alloy speed-up

[Carl Franks]

I've discovered (by RTFM!) that Template::Alloy's caching isn't on by default.

To get it to cache the template files, you need to set either
COMPILE_DIR or COMPILE_EXT

If you're running under a persistent environment, you should probably
also set COMPILE_PERL to compile the cached templates down to perl
code.

    render_class_args:
      COMPILE_DIR: /tmp
      COMPILE_PERL: 1

I've added this to the FAQ.

Carl