Get Async backend running
Logging for Async
typo in _oasis
enable platform debugging output
async: Fix multi-switch bug in controller, api tweak

The previous implementation of Async_Controller did not work on a
network with more than one switch. The stream of policies was being
shared between each "logical switch thread", which meant that when one
switch read the latest policy, no other switch would see it.

The fix is to use an intermediate pub/sub abstraction in the from of
Async_extra.Bus. This will guarantee that all subscribes will receive
published values. By blocking on the Bus.flushed deferred, the code also
ensure that that switches update their policies in lockstep.

The API for the controller has changed so as to require an initial
policy.
async: Add start_static for static policy controllers

At the moment, most of our testing's done with a single policy in mind.
start_static takes this into account by not requiring you to build a
stream for no reason.
async: Update to use lastest Highlevel API
async: update travis-ci with new dependencies
async: fix False constants in _oasis
async: update travis-ci to build async library
async: Eliminate remnants of Lwt
async: install openflow.async package in travis-ci
async: add missing textutil dependency for ocaml-openflow
async: update build script

Uses opam-bleeding to handle dependencies of dependencies, and adds IRC
notifications as well!
async: Use latest openflow.async API

Some modules got shuffled around.
saner Makefile and tweaks to _oasis
a simple policy
make tests run without running core tests
a topology that helps debug fast failover
async: Increase file descriptor limit for async

The file descriptor limit seems to be set to 1024 by async. This commit
makes katnetic use a different entry point for the scheduler, which
allows the user to configure the maximum number of file descriptors.

Related to frenetic-lang/ocaml-openflow#70.