Add boris as a dev dependency.

Having boris will allow the app skeleton to provide a REPL on platforms
supported by boris. Right now windows is not one of those platforms, but
I've been unable to find a good REPL for windows.

Refs #11
Remove file headers.
Add a basic REPL to the skeleton.

Include some help and error handling for boris not being installed.

Refs #11
Rename ReplShell to ConsoleShell.
Loosen requirements on boris.
Merge pull request #15 from cakephp/add-repl

Add a REPL to the app skeleton