Type definitions for typescript

[rodrigoelp]

Hi, browsing the library (as we use it) I couldn't help to notice you don't have type definitions for it (and we generated it a while back).

Would you be interested in these definitions? I'm also working on adding deviceIdentifier() which would be returning a promise with a string.

[rodrigoelp]

Hi, I've created #5 containing some of the changes we have done from your code. Let me know if you have comments.