* convert existing Cask:: namespace to Hbc::
* move Homebrew-fork code under Hbc::
* move freestanding classes such as Tty and TopologicalHash under Hbc::
* recast HOMEBREW_CASK_ constants as HBC_
* modify our Homebrew Formula for backward compatibility
* devscripts and dev docs
- add new file "cask/utils.rb" analogous to "utils.rb" in Homebrew
- define odebug and odumpcask, analogs of ohai and friends, but
which only give output when --debug is in effect
- move the debug setting from an instance variable in Cask::CLI
to a method Cask.debug, defined in "lib/cask/options.rb", which
was added in #2276. (Perhaps options.rb should be merged back
into Cask::CLI).
- sprinkle odebug statements liberally throughout the codebase
- update tests