Update Indicator example to 2.1 representation.

README.rst

@@ -33,7 +33,7 @@ be set automatically if not provided as keyword arguments.
     from stix2 import Indicator
 
     indicator = Indicator(name="File hash for malware variant",
-                          labels=["malicious-activity"],
+                          indicator_types=["malicious-activity"],
                           pattern="[file:hashes.md5 = 'd41d8cd98f00b204e9800998ecf8427e']")
 
 To parse a STIX JSON string into a Python STIX object, use ``parse()``:
@@ -44,13 +44,14 @@ To parse a STIX JSON string into a Python STIX object, use ``parse()``:
 
     indicator = parse("""{
         "type": "indicator",
+        "spec_version": "2.1",
         "id": "indicator--dbcbd659-c927-4f9a-994f-0a2632274394",
         "created": "2017-09-26T23:33:39.829Z",
         "modified": "2017-09-26T23:33:39.829Z",
-        "labels": [
+        "name": "File hash for malware variant",
+        "indicator_types": [
             "malicious-activity"
         ],
-        "name": "File hash for malware variant",
         "pattern": "[file:hashes.md5 ='d41d8cd98f00b204e9800998ecf8427e']",
         "valid_from": "2017-09-26T23:33:39.829952Z"
     }""")