Gracefully handle template literal properties in the parser

``` TypeScript var x = { a: "Hello" `b`: 123 } ``` Right now, the parser encounters the template string, decides it should bail out of object literal parsing, and we more or less recover thinking we have something like the following: ``` TypeScript var x = ({ a: "Hello" } `b`) : 123 } ``` So we'll report an error on what we think is: ``` TypeScript { a: "Hello" } `b` ``` - On the syntactic layer under ES5 mode, we'll say tagged templates are not supported unless in ES6. - On the semantic layer, we'll say `{ a: "Hello" }` is not invokable.