Sync and exception fixes

Adds `synchronous` keyword argument to `Connection` constructor, which makes
the connection behave as if it were synchronous, no matter the underlying
transport type. Useful for gevent were one does not want to use callbacks.
Applies to all channels, enforces `nowait=False` where applicable. For
gevent connections, imposes a minimum 1ms latency on synchronous methods when
there's a separate greenlet running `Connection.read_frames`.

Adds `synchronous` keyword argument to `Connection.channel`, which makes the
`Channel` object synchronous independent of the underlying transport type.
For example, if a synchronous channel on an asynchronous transport has a
protocol method called with `nowait=False` (where applicable), then the method
will not return until the response frame has been read. Does not enforce
`nowait=False` where applicable.

Adds `synchronous_connect` option to Connection constructor which will enforce
synchronous behavior in `Connection.connect` regardless of the underlying
transport type. Improves features to handle issue #7. Also makes
`Connection.close` synchronous. Defaults to True if transport is synchronous
or `synchronous=True` passed in constructor.
https://github.com/agoragames/haigha/issues/7

Standard and gevent socket transport will raise EnvironmentErrors that aren't
in `(errno.EAGAIN,errno.EWOULDBLOCK,errno.EINTR)`. Fixes notifying read loops
of potential problems and fixes #44

Immediately close connection and raise ConnectionClosed if there is a
FrameError in reading frames from the broker in `Connection.read_frames`.

Detect frames that are larger than negotiated frame max in
`Connection.send_frame`, immediately close connection and raise
ConnectionClosed.

Add property `Connection.closed`