#137 - Initial support for link templates.

Added LinkTemplate domain type that can deal with URI templates as defined in http://tools.ietf.org/html/rfc6570. We currently support /, ?, & and # variables up to level 3 of the spec (multiple parameter definitions). The templates can be expanded to a Link instance.

Added the necessary HAL mixins to render the instances as specified.
#131 - Prepare feature branch.
Hacking.