Update Go versions on Travis (#41)

diff --git a/.travis.yml b/.travis.yml
index 5895722..762d22c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,9 +3,11 @@
 go_import_path: go.uber.org/atomic
 
 go:
-  - 1.7
-  - 1.8
-  - 1.9
+  - 1.7.x
+  - 1.8.x
+  - 1.9.x
+  - 1.10.x
+  - 1.x # latest release
 
 cache:
   directories: