feat(Binding): improve errors - #4360

@vicb what do you think about adding "positive" cases as well? It probably doesn't belong here but currently https://github.com/angular/angular/blob/master/modules/angular2/src/core/facade/lang.ts doesn't have proper tests for isFunction / isClass.

Unless we assume that those utils are sufficiently tested by all the other tests in the ng2 codebase.

LGTM otherwise, feel free to merge if you think that more tests wouldn't add much here.

Oh, and BTW, I guess this check makes sense only for people using ES5/ES6, right? Since both Dart and TS should catch this, no? So I guess we should have some policy on those checks?

Merging PR #4360 on behalf of @vicb to branch presubmit-vicb-pr-4360.

@pkozlowski-opensource yep the check only makes sense for ES5 & ES6

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