Revert "Don't override the Go version, now that 1.5 has been released."
Revert "Don't override the Go version, now that 1.5 has been released."

I guess Travis hasn't updated its default; I still get 1.4.1.

This reverts commit 728cd4758886c7d1d25750b900010975116d0d09.

GoogleCloudPlatform/gcsfuse,kahing/gcsfuse,GoogleCloudPlatform/gcsfuse,mbrukman/gcsfuse,GoogleCloudPlatform/gcsfuse