travis: add OTP releases 20/21

kongo2002 · kongo2002 · commit 8f9194e1fb1a · 2018-07-22T22:32:40.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -9,6 +9,8 @@ cache:
   directories:
   - $HOME/.cache/rebar3/
 otp_release:
+- 21.0
+- 20.2
 - 19.3
 - 19.0
 - 18.3
