[cleanup, scope] Moved attr_reader to after includes
[cleanup, presentation_dsl] Send messages to @config via accessor
[cleanup, presentation] Stopped passing empty, unknown hash
[clean] Stopped using RevealCK::LOCATION. Now using RevealCK.path_to.
[cleanup] Added spec for RakeAware
[cleanup] Added spec for CreationTask
[cleanup] Added name implementation in CreationTask
[cleanup] Remove name from all CreationTask subclasses
[cleanup] Added CopyFilesTask

Not used anywhere, yet.

In anticipation of replacing these:

* copy_reveal_js.rb
* copy_user_files.rb
[cleanup] Removed unnecessary require
[cleanup] CreationTask no longer invokes "setup" in initializer

Removed this because..

 * it was hard to test.
 * Unsure of whether or not constructors should invoke behavior like
   this (immediately

The idea of "setup" and subclasses still exists. It's trigger by calling
"prepare" now.
[cleanup] Refactored spec for CopyFilesTask

I think this is better because it presumes *less* about the ultimate
destination of the messages and is instead based on only verifying the
"outgoing" message initiation on CopyFilesTask.

It does this because it assumes that a CopyFilesTask is "RakeAware" and
"RakeAware" has independently been verified to work with a
Rake::Application.

It also reads better.
[cleanup] Replaced CopyUserFiles, CopyRevealJs with CopyFileTask

* RevealJsFiles and UserFiles are now match the duck of FileListing
* SlideBuilder now creates these ducks and hands them off to distinct
  instances of CopyFilesTask.
Refactor. No functional code change.

* cleanup:
  [cleanup] Replaced CopyUserFiles, CopyRevealJs with CopyFileTask
  [cleanup] Refactored spec for CopyFilesTask
  [cleanup] CreationTask no longer invokes "setup" in initializer
  [cleanup] Removed unnecessary require
  [cleanup] Added CopyFilesTask
  [cleanup] Remove name from all CreationTask subclasses
  [cleanup] Added name implementation in CreationTask
  [cleanup] Added spec for CreationTask
  [cleanup] Added spec for RakeAware
  [clean] Stopped using RevealCK::LOCATION. Now using RevealCK.path_to.
  [cleanup, presentation] Stopped passing empty, unknown hash
  [cleanup, presentation_dsl] Send messages to @config via accessor
  [cleanup, scope] Moved attr_reader to after includes