Fix problem with errors not throwing the error callback in windows.

[Eeems]

Had to create a new PR for #52 as I had deleted the fork where the original PR came from.
From the original PR:

On windows when attempting to open pdf files Windows.System.Launcher.launchFileAsync() is throwing the following error: "The parameter is incorrect"
This error is not running the callback error due to not being caught by the promise handler. Adding a try/catch will solve this and at least allow the error to bubble up to the users code and allow them to debug it easier.
Should at least help with #51 but not fix it.

[shnist]

@Eeems thanks for doing this.