travis: 1.6.1 -> 1.6.2
travis: 1.6.1 -> 1.6.2

https://golang.org/doc/devel/release.html#go1.6.minor says it was
released on April 20

robphoenix/exercism-go,leenipper/xgo,exercism/xgo,leenipper/xgo,exercism/xgo,robphoenix/exercism-go