fix travis build

.travis.yml

@@ -1,7 +1,7 @@
 language: erlang
 otp_release:
-  - 19.3
-  - 20.3.8
+  - 21.0
+  - 22.0
 script:
   - "curl -fsSL https://raw.github.com/synrc/mad/master/mad > mad"
   - "chmod +x mad"