Make Node Manager's lock path vary with its main znode.

This allows a single ZooKeeper cluster to support the management
of multiple sets of Redis servers that are isolated from each other.
Merge pull request #28 from Bira/flexible_lock_path

Make Node Manager's lock path vary with its main znode.
Add note to changelog
new redis_failover features: master_only option, safe_mode option, on_node_change callback
only register for callback if in safe_mode
relax dependency on redis version
fix on_node_change callback values
add public current_master/current_slaves accessors; improve notification callback
properly handle nil slaves
update changelog
redis_node_manager should start if no redis servers are available (#29)
Directs all read/write operations to master
Different gemspec
Merge remote-tracking branch 'upstream/master'

Conflicts:
	lib/redis_failover/client.rb
Bumps version
add specs for :safe_mode and :master_only
readme update
Revert "readme update"

This reverts commit 11f2efa2037d08563e62a019ed51f4dfc9ab3611.
update gemspec description
etter handling of ZK session expirations in Node Manager