chore: switch from concurrently to npm-run-all

[wardbell]

See PR #54 which I accidentally merged prematurely.

STILL not ready to do it ... and if we did, should also update all of angular.io accordingly.

Too much work for too little reward at this time.

[khalillechelt]

If you ever decide to switch to npm-run-all I am happy to help with it.

[filipesilva]

Made obsolete by #158

Concurrently has the --kill-all functionality that was previously broken on windows/mac, but now is fixed. It is used for the e2e and unit tests on travis.

[wardbell]

Thanks, @Kahlil, but we're going to stick with concurrently.

Here's why (per one of our authors):

We need functionality from concurrently. It's not just a matter or looking better.

It's the --kill-others --success first flags we added in PR #158
--kill-others will terminate the other processes when the first finishes
--success first will give the status code of the first process to finish

These two together allow concurrently \"http-server -s\" \"protractor protractor.config.js\" --kill-others --success first" which means "run http-server and protractor at the same time, and once protractor is done kill off http-server"