HACKING doc re: `brew cask upgrade`

with issue tracking link
doc: Canonical name == App bundle name

There's only one substantive change in this patch, which is
that the Canonical App name is defined exactly by the name
of the App bundle on disk. The suggestion that the author's
website be consulted for orthography is removed.
add back ksdiff.rb for App store users

per a suggestion from @chrisopedia in ongoing discussion on #2276
remove md5 checksum support

Following up on #2719.  MD5 checksums are
* nowhere mentioned in our docs
* not used in any existing Cask
* deprecated in Homebrew
Therefore it seems sensible to delete this code.
FakeSystemCommand.run! should follow usual case
enforce valid values for :stderr on command.run
Added SpiderOak

SpiderOak provides an easy, secure and consolidated free online backup,
storage, access, sharing & sync tool for Windows, Mac OS X, and Linux
(Ubuntu, Debian & Fedora). SpiderOak offers a different approach to
online backup, synchronization, and sharing. This difference is not
just measured in our zero-knowledge privacy policy - the first one ever
employed in this setting - but also in our flexible design in handling
data from all platforms (Mac, Windows, Linux) and locations (external
drives, network volumes, USB keys) in one centralized account.
Added Ubuntu One

Ubuntu One is the personal cloud service that simplifies your digital
life. Imagine buying music and getting it delivered to the computers of
your choice. Or synchronizing your files and notes and accessing them
from anywhere. Or consolidating your computer and mobile phone contacts
and safely sharing documents and pictures with them. Ubuntu One can
already do this and more.
Added Launchy

Launchy is a free cross-platform utility designed to help you forget
about your start menu, the icons on your desktop, and even your file
manager.

Launchy indexes the programs in your start menu and can launch your
documents, project files, folders, and bookmarks with just a few
keystrokes!
Merge pull request #2978 from alebcay/ubuntu-one

Added Ubuntu One
Merge pull request #2976 from alebcay/launchy

Added Launchy
Merge pull request #2977 from alebcay/spideroak

Added SpiderOak
Reverted Chromium to the latest stable version
Tor Browser 3.5.2.1
Merge pull request #2975 from lowski/revert_chromium_to_stable

Reverted Chromium to the latest stable version
Merge pull request #2980 from miguelfrde/tor-browser

Tor Browser 3.5.2.1
Added Double Commander

Double Commander is a cross platform open source file manager with two
panels side by side. It is inspired by Total Commander and features
some new ideas.
Added Battle for Wesnoth

The Battle for Wesnoth is a Free, turn-based tactical strategy game
with a high fantasy theme, featuring both single-player, and
online/hotseat multiplayer combat.
Merge pull request #2982 from alebcay/battle-for-wesnoth

Added Battle for Wesnoth
Merge pull request #2981 from alebcay/double-commander

Added Double Commander