partial support for Closure Compiler types (#152)

introduces a real parser for Closure Compiler types, and uses the
parser to interpret type expressions in JSDoc tags.

TODO:
- provide a way to override the type expression
- update templateHelper to generate the correct links in type
applications

future enhancement (to be filed as a new issue): create pseudo-tags for
members that are described in the type expression (e.g., if the type
expression for the parameter `foo` is `{bar: string}`, add a tag for
`foo.bar` with no description)