Improved async/await support

I am Semih Okur, a PhD student in the CS department at the University of Illinois. I'm currently doing research on asynchronous programming in phone applications. I developed a tool that automatically improves async/await usages by doing transformations.

The tool found some opportunities in your application. First, it added "ConfigureAwait(false)" to some await statements in order to decrease overhead of capturing the context because those methods do not require context (like updating UI). 

Second, it added corresponding async calls of methods in JsonConvert class under "async" declared methods. For instance, it replaces "JsonConvert.DeserializeObject" with "JsonConvert.DeserializeObjectAsync". 

Are you interested in merging this pull request? If not, please let me know why, and I'll try and improve the pull request with your comments in mind.

Thanks,
Semih