Add additional commands to the admin client.

Added the following methods to the GearmanAdminClient class
  1. get_jobs methods is equivalent to gearadmin's '--show-jobs'
  2. get_unique_jobs method is equivalent to gearadmin's '--show-unique-jobs'
  3. get_pid methos is equivalent to gearadmin's '--getpid'
  4. cancel_job method is equivalent to gearadmin's '--cancel-job'

The get_jobs, get_unique_jobs and cancel_job protocols has not been
released yet.  These protocols are in 1.2 branch commited in
milestone: https://launchpad.net/gearmand/+milestone/1.1.6
Catch WANT_READ and WANT_WRITE SSL exceptions

SSL_ERROR_WANT_READ and SSL_ERROR_WANT_WRITE could possibly be
thrown from either recv() or send(), so we need to make sure both
are handled.
Don't remove entries from handle_to_request_map.
Since it's a WeakValueDict, no memory leak will be caused by not
removing entries, and in some cases entries are used even after
COMPLETE messages.

Fixes https://github.com/Yelp/python-gearman/issues/13
Merge pull request #55 from noamraph/master

Don't remove entries from handle_to_request_map.
Merge pull request #54 from Shrews/ssl_exc_fix

Catch WANT_READ and WANT_WRITE SSL exceptions
Merge pull request #34 from zaro0508/update-admin-client

Add additional commands to the admin client.
comment out^Cest failed due to pull #55
Merge branch 'master' of https://github.com/Yelp/python-gearman
remove more tests due to pull #55
Merge git://github.com/Yelp/python-gearman into keepalive