forgot to export matcher

lib/index.js

@@ -93,6 +93,7 @@ exports.cmdDefaults = {
 exports.aggregate = exports;
 
 //Expose these so that mungedb-aggregate can be extended.
+exports.matcher = require("./matcher/");
 exports.pipeline = require("./pipeline/");
 exports.query = require("./query/");
 exports.errors = require("./errors");