Fix systemjs-angular-loader.js for external templates (#444)

[feelingsofwhite]

these code changes are based on code found in the angular docs component with external testing downloadable example.

Although the refactoring I described in #444 seems pretty simple enough to understand, In my fork you can see branches demonstrate-bug-444 & demonstrate-fix-444 for more context of this bug and how this fix it.

I'm assuming because this code came from elsewhere in angular help/tutorial that it's okay.. but as a sidenote, the "indexof('moduleId')" seems rather poor because if you've got the word "moduleId" anywhere (for example, in a line of sourcecode you just commented out) it, the module fails to load the template. Not sure what the better solution would be, just my $0.02

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[feelingsofwhite]

I signed it!

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[Foxandxss]

Thanks. I am responsible for the changes but I forgot to update it here.

Yes, the indexOf is not the best solution, but does the trick for now.