allow multiple depends_on stanzas + refactor

also:
* disallow combining depends_on :macos comparison expressions
* ohai message when depends_on is present
* explicit accessors for :cask and :formula
* simplify some logic and flatten nested conditionals
* reflow incidental doc
DSL: add depends_on :x11
enable depends_on :arch in jaspersoft-studio
enable depends_on :arch in paraview
remove `caveats` / `x11_required`
enable Snow Leopard compatible version
enable latest Snow Leopard compatible version
enable Snow Leopard compatible version
Upgrade Steermouse.app to v4.2.2
depends_on OSX 10.9+ added for Fog Burner cask
add carthage
Merge pull request #7875 from wickedsp1d3r/steermouse

Upgrade Steermouse.app to v4.2.2
Updates the version for tagspaces and adds support for the 32 and 64 bit versions for OSX
Merge pull request #7885 from exherb/carthage

add carthage
Merge pull request #7877 from radeksimko/fog-burner-fix

Add depends_on OSX 10.9+ for Fog Burner cask
Add Playlist Assist.app version 1.2.1

Playlist Assist is a floating window to which tracks from iTunes can be dragged and then sorted, arranged, auditioned, edited, exported as text, and saved back to iTunes as a new playlist.
Add Dupin.app version 2.8.2

Now there's Dupin. Your iTunes duplicates manager.
Add Join Together.app version 7.2.0

Join Together will create and export a single AAC or ALAC audio file from the audio data of tracks dragged from iTunes or files dragged from the Finder.
Update filebot.rb

Release FileBot 4.5.3
Add M3Unify version 1.1.1

Stuff a thumb-drive with songs from your iTunes library.