Fix to properly check for 'undefined'

[andr3nun3s]

Still working on issue #89, just to make sure I'm on the right track as I've pinpointed every file in Source/Core that needs to be fixed.

[pjcozzi]

@Andre-Nunes these look good, thanks. The only thing that sticks out to me is that the formatting for define([... you have is slightly different than what we use elsewhere.

You are welcome to keep this pull request open and continue to commit to your branch until you are ready for a larger review.

[andr3nun3s]

Ok, I'll fix the formatting. I'll keep commiting untill all the files I've pinpointed are fixed.

[andr3nun3s]

Ok, I'm done with Core/, I've noticed #694 so I guess I should hold off on this issue until both pull requests are sorted.

Let me know if something comes up.

[mramato]

Thanks a lot @Andre-Nunes! This cleanup is long overdue and it's nice to see you taking charge of it.

[mramato]

@Andre-Nunes I don't know if you noticed my mailing list email, but it turns our there were still some problems with your branch that I didn't pick up. I fixed them (since I was the one that took them into master before they were ready) but I wanted to provide you some additional feedback anyway.

1. Before you open a pull request, always run ant jsHint on the command line. This should spit out any coding errors that you might have missed.
2. Always run the full unit tests and make sure there are no failures. If there are failures, compare them with the same tests running in Cesium master to determine if the failures are specific to your branch or not.

Anyway, thanks again for the changes and I'm sorry for the confusion! I look forward to more pull requests from you in the future.

[andr3nun3s]

Thanks for being so cool about it. I will keep that in mind for the future!

[pjcozzi]

Thanks @Andre-Nunes. These are good changes, and many are complimentary to #694.