Arcus Server 1.11.0

* [Feature] Support long key. KEY_MAX_LENGTH(250 => 32000).
* [Feature] Use space separated keys instead of comma separated keys.
* [Feature] Add a new mget command, efficient for getting multiple items.
* [Fix]     Fix the trimmed/duplicated bugs of bop smget.
* [Enhance] Use memory blocks to reduce alloc/free some large memory.

Arcus Server 1.10.3

* [Feature] leave and rejoin when cache_list znode is deleted.
* [Feature] Change the name of mcfailstop to zkfailstop.
* [Fix] the miscaculated checked value in tokenize_command().

Arcus Server 1.10.2

* [Feature] Add memcached failstop on/off configuration.
   - default is memcached failstop on.
* [Feature] Use zkensemble command separated from config command.
   - To support various operations on ZK ensemble.
* [Enhance] Generate log messages when available space becomes scarce.

Arcus Server 1.10.1

* [Enhancement] Alleviate excessive evictions.
   - Use the free small space if possible in space shortage status.
   - Use 99% of used space to separate the free smalli/avail space.
* [Other] Fix typos on docs.

Arcus Server 1.10.0

* [Feature] Added a map collection type.
* [Feature] Showed the current prefix count with stats command.
* [Feature] Combined the commands for getting/setting configuration
            into a single config command.
* [Feature] Set the maximum sticky memory with sticky_limit config.
* [Feature] Printed the invalid command if bad commad error occurs.
* [Feature] Stopped cache node if more than one server mapping znodes exist.
* [Fix] Fixed key dump bugs such as memory leak, duplicate dump, etc.
* [Fix] Fixed the negative free_chunk_space problem.
* [Enhancement] Reduced excessive evictions by adjusting sm classes.
* [Enhancement] Enhanced set performance by using prefix pointer
                when check invalid items.
* [Internal] Managed engine source code with separate engine directories.
* [Internal] Added the demo engine for use as a reference engine.
* [Internal] Performed the preparation task for long key support.
* [Internal] Performed ZK operation outside of zk watcher with a separate thread.
* [Internal] Added/used a scan facility to scan items in hash table.
* [Internal] Modified the ketama hash ring structure more usefully.
* [Other] Extensive minor enhancements.
* [Other] Extensive code refactoring.