Update Travis-CI Matrix

Apparently Travis-CI has dropped some of the older Erlang versions. I've
also added a run on 22.x

.travis.yml

@@ -3,19 +3,10 @@ notifications:
   email: paul.joseph.davis@gmail.com
 script: make check
 otp_release:
-   - 21.0
-   - 20.0
+   - 22.2.4
+   - 21.3.8.1
+   - 20.3.8.22
    - 19.3
-   - 19.2
-   - 19.1
-   - 19.0
    - 18.3
-   - 18.2
    - 17.5
-   - 17.4
    - R16B03-1
-   - R16B02
-   - R15B03
-   - R15B02
-   - R14B04
-   - R14B03