Bump version of golang in travis to v1.10

The http2 package removed support for v1.8 in,
https://github.com/golang/net/commit/22700d5518f6200cd1355b9d417285458095e8da

and it says 1.9 isn't actively tested.

.travis.yml

@@ -12,7 +12,7 @@ addons:
             - gcc-5
 
 go:
-    - 1.8.3
+    - 1.10.x
 
 env:
     - TRAVIS_NODE_VERSION="4.2" CC="gcc-5" CXX="g++-5"