Update CI to use currently-supported Go versions
diff --git a/.travis.yml b/.travis.yml
index 5743a0c..3ddfb8a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,10 +1,8 @@
 language: go
 
 go:
-  - "1.10.x"
-  - "1.11.x"
-  - "1.12.x"
-  - "master"
+  - "1.14.x"
+  - "1.15.x"
 
 arch:
   - amd64