Run lint over all ts files

[EvanBoyle]

https://github.com/pulumi/examples/blob/master/Makefile#L14

This only hits the first level of *.ts files in the next directory level. If you run tslint -c tslint.json '**/*.ts' it runs over all nested subdirectories. I would just make this change, but it then we start hitting all of the nested node_modules. The --exclude flag doesn't seem to help here. I was able to find an open bug on this, but it's noted that TSLint is deprecated: https://github.com/palantir/tslint/issues/4768

Our fix here should be to migrate to ESLint and make sure we update command to lint all nested TS files: https://github.com/pulumi/examples/issues/520