Prepare for relase: Add CHANGES entry for v2.1

CHANGES

@@ -1,3 +1,36 @@
+Version 2.1 (in development)
+============================
+
+* New features:
+
+  - `json_loadb()`: Decode a string with a given size, useful if the
+    string is not null terminated.
+
+  - Add JSON_ENCODE_ANY encoding flag to allow encoding any JSON
+    value. By default, only arrays and objects can be encoded. (#19)
+
+  - Add JSON_REJECT_DUPLICATES decoding flag to issue a decoding error
+    if any JSON object in the input contins duplicate keys. (#3)
+
+  - Add JSON_DISABLE_EOF_CHECK decoding flag to stop decoding after a
+    valid JSON input. This allows other data after the JSON data.
+
+* Bug fixes:
+
+  - Fix an additional memory leak when memory allocation fails in
+    `json_object_set()` and friends.
+
+  - Clear errno before calling `strtod()` for better portability. (#27)
+
+* Building:
+
+  - Avoid set-but-not-used warning/error in a test. (#20)
+
+* Other:
+
+  - Minor clarifications to documentation.
+
+
 Version 2.0.1
 =============