Add support for new Angular 2 Forms

[platosha]

Fixes #43

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This change is

[tehapo]

Looks like this PR does not compile anymore against Angular 2.0.0-rc.5 version.

src/polymer-element.spec.ts(2,1): error TS2305: Module '"[clip]@angular/core/testing"' has no exported member 'describe'.
src/polymer-element.spec.ts(3,1): error TS2305: Module '"[clip]@angular/core/testing"' has no exported member 'expect'.
src/polymer-element.spec.ts(4,1): error TS2305: Module '"[clip]@angular/core/testing"' has no exported member 'it'.
src/polymer-element.spec.ts(10,10): error TS2305: Module '"[clip]@angular/compiler/testing"' has no exported member 'TestComponentBuilder'.
src/polymer-element.spec.ts(10,32): error TS2305: Module '"[clip]@angular/compiler/testing"' has no exported member 'ComponentFixture'.
src/polymer-element.spec.ts(207,11): error TS2346: Supplied parameters do not match any signature of call target.

I can take a look at this and add a commit to fix this.

[manolo]

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Reviewed 5 of 5 files at r2.
Review status: all files reviewed at latest revision, all discussions resolved.

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