DOC: add convert: true example in g1.types docs, fixes #139

docs/types.md

@@ -4,10 +4,12 @@
 
 ```js
 var data = [
-  {a: 1, b: 1.1, c: 'c', d: '2014-04-04', e: true},
+  {a: 1, b: 1.1, c: 'c', d: '2014-04-04', e: true, f: new Date()},
   {a: 2, b: 2},
 ]
-g1.types(data)      // Returns {"a": "number", "b": "number", "c": "string", "d": "date", "e": "boolean"}
+g.types(data)                   // {"a":"number","b":"number","c":"string","d":"string","e":"boolean","f":"date"}
+g1.types(data, {convert: true})   // {"a":"number","b":"number","c":"string","d":"date","e":"boolean","f":"date"}
+
 ```
 
 ## g1.types options