Cross-platform http client wrapper for review, now for mac/ios only

I have a couple questions about the usage of ```class HttpClient```.

1. If ```Connect()``` does all the job, can there be a better name?
2. If it's a one-time class, perhaps a better design idea might go along the lines of ```HttpDownloadedFile file = HttpClient::FetchURL(url);```, with all disabled default and enabled move constructor magic to indicate its one-time nature?