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
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
Added BugHub

BugHub is a GitHub client focused on assisting software developers in
viewing and processing issues and pull requests.
Merge pull request #2983 from alebcay/bughub

Added BugHub
Add Recordit.app
Merge pull request #2974 from ddinh/recordit

Add Recordit.app v1.0
Add WeiboX.app v2.6.1
KeyRemap4MacBook 9.3.0