Move inner classes to individual files
Run tests with rake testtask
Move At specs to at_test
Move option specs to each describe block
Move event managemenent logic to Manager
Use manager's config
Move functions to Manager from Clockwork

Clockwork module has only the features useful.
This patch reduces the name conflict problem with other gems adding methods to global namespace.
Merge branch 'split_module'
Add MIT License specification to gemspec

Thanks to @bf4's detailed description (#49).
Remove note added in e503377283d6da742f38de03e2a9ea5efddfd9f4

Because clockwork no longer exposes `register` method to
global namespace, this workaround is not necessary.

Including Clockwork adds following methods.
In case there are methods with the same name in global namespace, continue to use this technique.

- configure
- handler
- every
- run
- clear!
Version 0.6.0

Changes:

  Refactor clockwork.rb and split into class files.

  Move event dispatch manager to Clockwork::Manager class.

  Reduce global namespace taint

  Explicitly specify the license in gemspec