Test with OTP releases 18.3, 19, 3 and 20.3

the latest of each of the above major releases.

diff --git a/.travis.yml b/.travis.yml
index 9f834a9..4cd9621 100644 (file)
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,6 +12,9 @@ otp_release:
     - 21.2
     - 21.1
     - 21.0
+    - 20.3
+    - 19.3
+    - 18.3
     - 18.1
     - 18.0
     - 17.5