Add definition for Object.entries and Object.values in lib.es2017.d.ts

The proposal is at stage 4 now. here is the spec: https://github.com/tc39/proposal-object-values-entries

here is the definition skeleton:

``` ts
interface ObjectConstructor {
    keys(o: any): string[];
    values<T>(o: { [s: string]: T }): T[];
    values(o: any): any[];
    entries<T>(o: { [s: string]: T }): [string, T][];
    entries(o: any): [string, any][];
}
```
