Prepare for 2.13.0 release.

CHANGELOG.md

-# Changes in version 2.13.0 - 2020-??-??
+# Changes in version 2.13.0 - 2020-05-16
 
  * Medium changes
+   - Parse OnionPerf analysis results format version 2.0.
    - Extend Torperf results to provide partial download times for 10,
      20, 50, 100, 200, and 500 KiB as well as 1, 2, and 5 MiB.
 

build.xml

@@ -7,7 +7,7 @@
 <project default="usage" name="metrics-lib" basedir="."
          xmlns:ivy="antlib:org.apache.ivy.ant">
 
-  <property name="release.version" value="2.12.2-dev" />
+  <property name="release.version" value="2.13.0" />
   <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" />