feat(jsdoc package): use jsdoc rather than js doc-extractor

The `jsdoc` doc-extractor is compatible with the `js` version but provides
additional functionality.  The code following the jsdoc comment block
is provided to the doc as an extra property that can be used by successive
doc-processors.  For instance, to extract the name of the described code
item if no @name tag is provided.

Author: petebacondarwin

jsdoc/index.js

@@ -1,6 +1,6 @@
 module.exports = function(config) {
 
-  config.append('source.extractors', require('./extractors/js'));
+  config.append('source.extractors', require('./extractors/jsdoc'));
 
   config.append('processing.processors', [
     require('./processors/doc-extractor'),