Downgrade CaskAlreadyInstalledError to a warning

Automatic installs - like thoughtbot's laptop script - fail when we
use Homebrew's onoe method.  Using opoo (to warn) will let the
scripts complete successfully when they try to install packages that
have already been installed.

Test for downgrading AlreadyInstalledError to warning
re-use version in cycling74-max.rb
re-use version in dwarf-fortress.rb
re-use version in epub-to-pdf.rb
re-use version in p4v.rb
re-use version in pngyu.rb
re-use version in qqinput.rb

and add UTF-8 encoding comment for older Rubies
re-use version in reaper.rb
re-use version in rekordbox.rb
re-use version in silo.rb
Update cocktail to 8.0 (Yosemite edition)
Update iexplorer
Add SSLMate
Merge pull request #6836 from rolandwalker/reuse_versions

Reuse version in 9 Casks
Merge pull request #6827 from jamesottaway/sslmate

Add SSLMate
Merge pull request #6850 from redondos/master

Update iexplorer
Merge pull request #6849 from fza/master

Update cocktail to 8.0 (Yosemite edition)
Update FlightGear to v3.2.0
Merge pull request #6851 from Ihavee/Ihavee

Upgrade shadowsocksx to 2.3
Merge pull request #6852 from alebcay/flightgear

Update FlightGear to v3.2.0