More detailed log messages around connections
Add timeouts to conn creation, blocking messages

Instead of waiting indefinitely for a new connection
to initialize, a timeout is used when blocking for the event.

Likewise, for blocking messages (used by the control connection
and when setting keyspaces), set a timeout to avoid blocking
indefinitely in corner cases.
Handle exceptions when erroring callbacks

In case any of the callbacks don't properly handle exceptions,
handle the exceptions (with a log message) and continue erroring
out the rest of the callbacks.

Related to #48
Don't close asyncore connection on empty read
Grace period before new conns can be trashed

New connections were frequently being trashed before enough
time had passed to put sufficient load on them.  This adds
a basic grace period during which new connections cannot
be trashed, regardless of how few operations they have
in flight.
Raise exception conn is closed mid-initialization
New run_in_executor decoractor for Cluster
Maintain listener list within Cluster
Avoid deadlock when nodes go up and down
Log at warn when a host is marked down
Update changelog, bump version to 1.0.0b6
Bump to post-release version
Update version notes in README-dev
Correctly set final exception when query fails on all hosts

Before this change, the Event that notifies listeners
that the operation has completed was not being triggered.
Define ResponseFuture.__repr__()
Prepare statements in chunks of 10

This helps to finish preparing all statements more quickly
when down nodes come back up.
Stop preparation of statements after one failure
Don't callback when reconnector is cancelled
Better cleanup of failed node up handling

When a node comes back up, we try to create a new connection
pool for it.  If that process fails, listeners and the
control connection need to be notified.  Prior to this change,
they would not, so the pool could remain in a shutdown state
and the control connection could be unaware that its connection
had failed.
Correct str len type for murmur3 key

Without the PY_SSIZE_T_CLEAN macro defined, the length
of the key is set as an int* instead of a Py_ssize_t