Introduce GPG operations

Add methods for cryptographic authentication of Cask packages with
the GPG software suite.

Homebrew Cask invokes the system-standard `gpg` binary to import
keys to the GPG keychain, download signatures to versioned metadata
folders, and verify packages. Homebrew Cask aborts if any step fails.

GPG verification is not currently invoked during the audit or
installation processes, and is intentionally left undocumented.

Example usage:
    gpg = Cask::GpgCheck.new(cask)
    gpg.verify(package_archive_path) if gpg.available
Update NoSleep to 1.4.0
eclipse-ide: fix wrong sha256
Merge pull request #7579 from xu-cheng/eclipse-ide

eclipse-ide: fix wrong sha256
Update julia to 0.3.3
Merge pull request #7581 from ndr-qef/casks/julia

Update julia to 0.3.3
doc: move `stage_only` to the artifacts section

* `stage_only` is a pseudo-artifact
* satisfies the doc that "At Least One Artifact Stanza Is Also Required"
doc nit: consistency of case in table cells

with some trivial changes for shorter wording
rename faux-pas.rb to fauxpas.rb

to conform with naming conventions
rename folding-text.rb to foldingtext.rb

to conform with naming conventions
rename mass-replace-it.rb to massreplaceit.rb

to conform with naming conventions
rename mini-metro.rb to minimetro.rb

to conform with naming conventions
rename raw-therapee.rb to rawtherapee.rb

to conform with naming conventions
rename readefine-desktop.rb to readefine.rb

to conform with naming conventions
rename audio-mate.rb to audiomate.rb

to conform with naming conventions
rename odesk.rb to odesk-team.rb

to conform with naming conventions
rename glo.rb to glo-bible.rb

to conform with naming conventions
comment re: number in name, c3
comment re: number in name, fourk-youtube-to-mp3
comment re: number in name, icons8