Log Message:
Import rake.

Rake is a simple ruby build program with capabilities similar to make.
Rake has the following features:

  * Rakefiles (rake's version of Makefiles) are completely defined in
    standard Ruby syntax.  No XML files to edit.  No quirky Makefile
    syntax to worry about (is that a tab or a space?)
  * Users can specify tasks with prerequisites.
  * Rake supports rule patterns to sythesize implicit tasks.
  * Rake is lightweight.  It can be distributed with other projects as
    a single file.  Projects that depend upon rake do not require that
    rake be installed on target systems.