Prepare for 2.1.1 release.

CHANGELOG.md

-# Changes in version 2.?.? - 2017-??-??
+# Changes in version 2.1.1 - 2017-10-09
 
- * Medium changes
+ * Minor changes
    - Add new optional "build_revision" field to index.json with the
      Git revision supplied by the calling software.
 

build.xml

@@ -6,7 +6,7 @@
 
 <project default="usage" name="metrics-lib" basedir=".">
 
-  <property name="release.version" value="2.1.0-dev" />
+  <property name="release.version" value="2.1.1" />
   <property name="javadoc-title" value="Tor Metrics Library API Documentation"/>
   <property name="javadoc-excludes" value="**/impl/** **/index/** **/internal/** **/log/**" />
   <property name="implementation-title" value="Tor Metrics Library" />