Add ZendStudio

Add ZendServer

Update and rename zend-studio.rb to zendstudio.rb

Update and rename zend-server.rb to zendserver.rb
Merge pull request #3088 from ahbeng/vlc

VLC 2.1.4
Add DEVONThink Pro 2.7.3

Add cask for DEVONThink Pro 2.7.3
App complains about being installed in `~/Applications/` on first launch but this can be dismissed.
Update Widelands to Build 18
Add (unoffical) Google Music app v1.0.2
shrink CONTRIBUTING.md to 1/4 its current size

Rationale:
- lengthy CONTRIBUTING.md may itself discourage new Cask authors
- it is doubtful that everyone reads to the end, where there
  are important notes about squashing.

CONTRIBUTING.md reduced from 7947 words to 1927 words.

This was accomplished principally by spinning out "details" sections
into a new reference file `doc/THE_CASK_LANGUAGE.md`, but also by
ruthless re-organization, removal of duplication, and trimming of
phrases. Content remains 99% identical, though a few typos were
caught along the way, and a table of contents was added.
Merge pull request #3093 from kevinoconnor7/google-music

Add (unoffical) Google Music app v1.0.2
Merge pull request #3090 from deepj/widelands

Update Widelands to Build 18
add CLI binary for Golly.app
Merge pull request #3076 from rolandwalker/user_from_etc

more reliable way to look up username
Merge pull request #2931 from rolandwalker/remove_md5

remove md5 checksum support
Merge pull request #3091 from rolandwalker/golly_binary

add CLI binary for Golly.app
Merge pull request #3087 from ndr-qef/librecad

Add LibreCAD
Merge pull request #3078 from bingfoon/master

Add Zend Studio 10.6.0
remove OmniOutliner Pro Cask

closes #2777.  This was discontinued as a separate product.
fix broken URL for OmniWeb
the "latest" url contained a versioned subdir
fix broken app link for CLIX.app
fix broken URL for doubletwist.app
fix broken link for LogMeInIgnition