Add an option to bypass dist when running gulp e2e

[thaiat]

gulp e2e --skip-dist

gulp.task('e2e', 'Runs e2e tests.', function(done) {
    runSequence(
        ['webdriver-update', args.skipDist ? 'wait' : 'dist'],
        'e2e:serve',
        'e2e:run',
        done
    );
});