Prepare version 2.8.1

CHANGELOG.md

 Change Log
 ==========
 
+Version 2.8.1 *(2020-03-25)*
+----------------------------
+
+ * Fix: Do not access `MethodHandles.Lookup` on Android API 24 and 25. The class is only available
+   on Android API 26 and higher.
+
+
 Version 2.8.0 *(2020-03-23)*
 ----------------------------
 

README.md

@@ -9,7 +9,7 @@ For more information please see [the website][1].
 Download
 --------
 
-Download [the latest JAR][2] or grab from Maven central at the coordinates `com.squareup.retrofit2:retrofit:2.8.0`.
+Download [the latest JAR][2] or grab from Maven central at the coordinates `com.squareup.retrofit2:retrofit:2.8.1`.
 
 Snapshots of the development version are available in [Sonatype's `snapshots` repository][snap].