Compiler allows assignments to read-only properties

[mwisnicki]

http://typescript.codeplex.com/workitem/488

"use strict";
class SomeClass {
    public get someProperty(): string {
        return "some value";
    }
}
var someInstance = new SomeClass();
someInstance.someProperty = "another value"; //Run-time error. ECMAScript 5.1 - 11.13.1

[RyanCavanaugh]

Duplicate of #12

Defining a get-only accessor does not create a read-only property because TypeScript does not have a notion of read-only properties