File includes with 'add_include_paths' support.
Replaced 'die' calls with 'Carp::croak'.
More documentation on expressions, an essay basically.
Documented the (ok, a) final grammar.
Positron::Expression : first version

The first version of expressions, with a few tests.
Positron::DataTemplate uses Expression

All occurrances of $environment->get($this) replaced by
Positron::Expression::evaluate($this, $environment).