Added remaining methods to the http client. Also removed main.cc file and created an examples/ folder

anymore.

The event-loop has now been extracted inside its own Io::Service
component which allows us to reuse it.
A new Io::ServiceGroup class has been introduced for multi-threaded
I/O. a ServiceGroup will spawn multiple Io::Service inside their own
thread. Every instance of Io::Service also has its own Io::Handler, the
handler is not shared between io threads.

A route can now be bound to a non member function. Also changed the API a litle bit to avoid big code duplication

Http::Endpoint: added a threaded serving mode that will spawn an acceptor thread rather than running in the same thread

Introduced a lock-free MPSC queue between the user and I/O thread to make sure that all I/O operations happen in the dedicated I/O thread

Listener: requestLoad does not return a resolved promise anymore but instead directly returns the result

Async: implemented a whenAny primitive that returns a Promise that will be resolved when one of the Promise is resolved