Update travis to run make build

Ensure all packages can be built, even those not yet imported by binaries.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

snapshot/testsuite/testsuite_unix.go

@@ -0,0 +1,12 @@
+// +build !windows
+
+package testsuite
+
+import "syscall"
+
+func clearMask() func() {
+	oldumask := syscall.Umask(0)
+	return func() {
+		syscall.Umask(oldumask)
+	}
+}