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
Use int, not byte, type for IO flags
Better error message for non-int consistency level
Fix bad consistency level on retries

On Read/WriteTimeouts, the operation would be retried with
the same consistency level as the previous operation, but that
consistency level was erroneously being stored as a string
instead of an int, resulting in errors like
"error: cannot convert argument to integer".
Revert "Better error message for non-int consistency level"

This reverts commit c7df51c6b571cab8dea02ca763f95de96d73a564.
Better error messages for failed stmt prepares
Prepare statements against all hosts in parallel
Fix async keyspace setting on connections

When keyspaces were set asynchronously for connections,
the connection wasn't properly recording the new keyspace,
which could lead to errors preparing statements and
unnecessary re-setting of the keyspace.
Define __str__ and __repr__ for Connection
More debug logging around connection management