Add finalizer :callback API.
Namespace thread locals (fixes #117)

This namespaces the four thread local names that Celluloid used
previously:

* :actor
* :mailbox
* :task
* :queue

...with celluloid_ on the front so as to avoid collisions:

* :celluloid_actor
* :celluloid_mailbox
* :celluloid_task
* :celluloid_queue
Bump version to 0.12.4.pre
Revert "Namespace thread locals (fixes #117)"

This reverts commit 2db76eb15338359374824df57c22ce2521e433bc.

This is incompatible with Celluloid::IO, etc
Bump version to 0.12.4.pre2
Bump version to 0.12.4
Merge pull request #119 from ileitch/finalizer

Add finalizer :callback API.
Namespace thread locals

This reverts c448598431bdd2859bbd1c76bc4f666b38d6dedf
Convert InternalPool to a class

See: https://twitter.com/bascule/status/278705954898464768
Update lib/celluloid/stack_dumper.rb

Fix incorrect object_id in output.
Bump version
Merge pull request #134 from mperham/patch-1

Update lib/celluloid/stack_dumper.rb
Clear thread locals from threads returned to the pool

Previously threads checked out of Celluloid's InternalPool which were
returned would leak their thread locals. While Ruby apparently lacks
an API to clear thread locals, we can do the next best thing by
setting them all to nil.

I look forward to Ruby 2.0's Better Thread Local API!
This feels less hacky than an ivar
Revert "Move guard-rspec out of CI gems"

This reverts commit 4175f4a31b66c71d1db421dd934f9fdcb4b840b8. This was an unjustified change.

Conflicts:
	Gemfile
o_O

These tests spontaneously broke for no apparent reason. RSpec insanity? Aaargh!

Anyway, changing "==" to "eq" seems to fix them.
Spec for blocks on synchronous calls
Spec for NoMethodErrors not crashing actors
Don't crash receivers on NoMethodErrors
Don't crash receivers on arity errors