- update metalsmith plugins for metalsmith 1.x
- json-schema-*: consider a different implementation strategy that makes "core" less core:
- does not require pre-parsing the schema in order to dereference and validate
- allows pluggable validators through a common interface, with a default validator
- parses the schema only when building a correlation, which is where it is actually used
- correlation prototype is extendable, as now, through a plugin interface
- "model" functionality is implemented as a correlation plugin