Fix `.ts` files being copied to the build dir (#325)
Fix `.ts` files being copied to the build dir (#325)

Before this change, running `gulp` would incorrectly copy `.ts`
test files to the `build/test` directory.
DominicKramer/cloud-debug-nodejs,matthewloring/cloud-debug-nodejs,googleapis/cloud-debug-nodejs,DominicKramer/cloud-debug-nodejs,googleapis/cloud-debug-nodejs,matthewloring/cloud-debug-nodejs,googleapis/cloud-debug-nodejs,DominicKramer/cloud-debug-nodejs,matthewloring/cloud-debug-nodejs