Buffered appender to bulk endpoint

Here's a first version of a buffered loggly appender.
I didn't rip the whole thing apart so there are actually some pieces of the original implementation left.
The buffered appender buffers and also has a timer that flushes the buffer after a while if log frequency is too low.

I had a TinyIoCContainer in there but it felt like overkill, what do you think?

@joem-iq @stefanmoser 
@stefanmoser Is that what you meant? Note that this does not block another flush while the other is still being **sent** because the send is async. But it does prevent the flush while we are serializing and calling the post.