It's been so long, I figured we should catch up. A year's worth of maintenance on twitter/zookeeper (take: 2)

For roughtly the past year I've been developing this codebase in my fork, and doing regular releases in support of the [ZK](https://github.com/slyphon/zk) gem. There are really too many changes to list here (it's been a year since the last pull request), from the CHANGELOG file here are some of the greatest hits:

    v0.9.2 More efficient and simpler wrappers for GIL release
    
      * After a code review by Andrew Wason (rectalogic), use a much simpler
        technique for creating the arg structs and passing them to the
        zkrb_gvl_* functions. No malloc(), no free(), no problem.
    
    v0.9.1 see v0.8.4 notes, same patch
    
    v0.9.0 RELEASE THE KRAK..er, GIL!!
    
      * In >= 1.9.2 the ruby interpreter allows you to release the GIL when
        calling into native code, sounds like a good idea.
        
        This release makes use of that code by parsing the zookeeper.h header file
        and extracting the method signatures of all relevant zoo_* functions, then
        generating boilerplate that allows us to call those functions via the
        rb_thread_blocking_region function.
    
        1.8.7 compatibility is maintained by stubbing out that functionality if built
        under 1.8.7. 
    
      * 1.8.7 is deprecated! I will continue to support 1.8.7 for the near future
        but sometime soon, you're gonna have to upgrade.
    
    v0.8.4 fix NameError, require 'forwardable'
      
      * Really not sure why this didn't come up in tests
    
      * issue here https://github.com/slyphon/zk/issues/22
    
    v0.8.3 fix NonLocalJump exception in event delivery thread shutdown code
    
      * hit a corner case where we're waiting for the zkc handle setup
        and the user decides to shutdown, but before we've had a chance
        to enter the delivery loop.
    
      * Cleaned up some nasty code in ZookeeperConstants
    
      * removed ZookeeperConstants#print_events and ZookeeperConstants#print_states
    
      * changed EVENT_TYPE_NAMES and EVENT_STATE_NAMES in ZookeeperConstants
        to use string values instead of symbols
    
    v0.8.2 fix close after a fork()
    
      * The dispatch thread will be dead in this situation, so we need to 
        check to see if it's already dead before waiting on it to exit.
    
    v0.8.1 Java client fix, silence warnings
    
    v0.8.0 Refactor C implementaion, EventMachine client
    
      * separated CZookeeper and ZookeeperBase implementation
      
        This solves issues with reopen not working properly, makes for a much
        cleaner event delivery implementation. ZookeeperBase controls the lifecycle
        of the event dispatch thread now, rather than it being tied to CZookeeper.
      
      * added support for the 'sync' API call
      
      * Refactored zookeeper_c.c and zookeeper_lib.c
      
        More error checking in zookeeper_lib.c and restructure some things to make
        logic easier to follow
      
        Fix bug in method_get_next_event that made the shutdown case so complicated
      
      * Massively simplified EMClient implementation
    
        Rather than trying to hook the IO used by zookeeper_lib to notify zookeeper_c
        about event availabiltiy directly into EventMachine, use the same event delivery
        thread, but wrap the dispatch call in EM.schedule.
    
      * Improve implementation of spin-lock-esque code that waits for the connection to be
        established before returning.
    
        This cut the test runtime down from 1m 20s to 2s.
    
      * Java client refactoring, similar correctness changes
    
      * Change ZookeeperException base class to StandardError instead of Exception


In addition, I've added a Gemfile, fixed chrooted connection behavior so that the C implementation matches the Java client, rake scripts for testing across 5 different ruby implementations (using rvm), and added lots more tests. 

I'm a committer on this project, so I'm going to let this pull request sit for a while, and if I don't hear any objections, I'm going to accept and merge it.