add fulltext operator

Author: Greg

README.md

@@ -287,6 +287,25 @@ Through the REST API:
 /messages?label[$overlap][0]=important&label[$overlap][1]=work&label[$overlap][2]=urgent
 ```
 
+### $fulltext
+
+For PostgreSQL only, for fulltext-indexed fields, finds records that match useing postgres' fulltext natural-langauge search. The following query retrieves all messages whose labels contain any of the values `important`, `work`, or `urgent`, but no values outside that list :
+
+```js
+app.service('messages').find({
+  query: {
+    labels: {
+      $contained_by: ['important', 'work', 'urgent']
+    }
+  }
+});
+```
+
+Through the REST API:
+
+```
+/messages?label[$contained_by][0]=important&label[$contained_by][1]=work&label[$contained_by][2]=urgent
+```
 
 ## Transaction Support
 

lib/index.js

@@ -26,7 +26,8 @@ const OPERATORS = {
   $ilike: 'ilike',
   $overlap: '&&',
   $contains: '@>',
-  $contained_by: '<@'
+  $contained_by: '<@',
+  $fulltext: '@@'
 };
 
 // Create the service.
@@ -45,7 +46,7 @@ class Service extends AdapterService {
     super(Object.assign({
       id: 'id'
     }, options, {
-        whitelist: whitelist.concat(['$like', '$notlike', '$ilike', '$and', '$overlap', '$contains', '$contained_by'])
+        whitelist: whitelist.concat(['$like', '$notlike', '$ilike', '$and', '$overlap', '$contains', '$contained_by', '$fulltext'])
       }));
 
     this.table = options.name;