Subtle errors in options passed to tsb.create() are ignored (not reported)

[BurtHarris]

For example:

const cjs = tsb.create({
  outDir: 'lib',
  module: 'commonjs',
  target: 'es5',
  declaration: true,
  lib: ['es5', 'es2015', 'dom'],
  sourcemap: true,
  experimentalDecorators: true
});

gulp-tsb reports no error, even though the sourceMap option has a capitalization error.