Minor Updates

I am not sure what the etiquette is around submitting pull requests as I am not really a developer by trade. That said, I have made a few very small tweaks to your library and thought I would share incase you are interested.

The first small tweak is letting the user set the 'sendImmediately' boolean themselves for requests to the hub. This gives a bit more control and seemed to resolve a problem I was having when interfacing with Superfeedr

The second small tweak was to the regular expression used to parse out the 'url' and 'rel' values from the header on POST (feed update). The previous version allowed for single quotes. This wasn't working with Superfeedr as they are now using double quotes.

I tired to update the documentation. I also tweaked the test to validate for the new option but I am not great at TDD yet so I may have missed something. 

If you have questions let me know.

Thanks,

Daniel