register_parser: Register a resource parser.
In syberia/director: Load, track, and manage dependencies in a file structure.

Description Usage Arguments Examples

1 2	register_parser(path, parser = function() { }, overwrite = FALSE, cache = FALSE)

`path`	character. The prefix to look for in the director.
`parser`	function.
`overwrite`	logical. If `TRUE`, `register_parser` will overwrite the route instead of erroring if the path already has a registered parser. The default is `FALSE`.
`cache`	logical. Whether or not to cache resources processed with this parser. Cached resources will not be re-parsed if their dependencies have not been modified. This distinction is important, as most resources are factory resources (the object they generate should not be shared across the entire project; instead, a copy should be made). The default is `FALSE`.

## Not run: 
  d <- director('some/project')
  d$register_parser('models', function() { print("I am a ", resource, ", a model!") })
  r <- d$resource('models/some_model.R')
  r$value() # Will print: I am a models/some_model, a model!

## End(Not run)