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
revise accessibility methods in postflight miniDSL

* rename `remove_accessibility_access` to `disable_accessibility_access`
  to match corresponding method `enable_accessibility_access`
* move `TCC.db` and `.AccessibilityAPIEnabled` paths to `Cask::Locations`
* remove unneeded backslash from `TCC.db` path
* use full paths to `touch` and `sqlite3` utilities
* use `@command.run` instead of `system_command` which is intended as an
  external interface
* reverse conditional so enable/disable logic is consistent
* `sudo` is needed when creating `.AccessibilityAPIEnabled`
* instead of silent fail, warn that access cannot be safely disabled on
  Mountain Lion and earlier (it could, but might affect other apps)
* quoting/whitespace
revise plist methods in postflight mini-DSL

* accept index argument to `info_plist` in case of multiple `app`
  artifacts, defaulting to first
* return `Pathname` object from `info_plist`
* use `@command.run` instead of `system_command` which is intended
  as an external interface
* quoting
revise move_to_app method in postflight mini-DSL

* use `@command.run` instead of `system_command` which is intended
  as an external interface
* quoting
Add cask for Avast Mac Security

Create a cask for Avast Mac Security. Not entirely sure if the
uninstall stanza is correct. The dmg comes with an uninstaller
with the filename 'com.avast.uninstall.app', but I can't find
anything in the docs about using a pre-packaged uninstaller.

Remove broken uninstall stanza

Add uninstall stanza suggested by @rolandwalker

This stanza seems to work. Application and support files all removed
after uninstall.
Add FingerLock.app version 1.0

FingerKey makes it easy to unlock your computer without having to type your password every time.
Update WD Security to 2.0.0.30
Merge pull request #7675 from jawshooah/add-avast-cask

Add cask for Avast Mac Security
Merge pull request #7687 from vinkla/fingerlock

Add FingerLock.app version 1.0
Add cask for WDFirmwareUpdater
Merge pull request #7689 from jawshooah/add-wd-firmware-updater

Add cask for WDFirmwareUpdater
Re-add the FreeSMUG Chromium build (latest version: 38.0.2125.122) as a separate cask,
which has also been adjusted to carry the new format (including license stanza)
Upgrade Vienna.app to v3.0.1 and add zap support
Update maintenance.rb
Merge pull request #7692 from dwihn0r/freesmug-chromium

Re-add the FreeSMUG Chromium build (latest version: 38.0.2125.122) as a ...
Merge pull request #7695 from josh64x2/vienna-update

Upgrade Vienna.app to v3.0.1 and add zap support
Merge pull request #7697 from jaaaaared/patch-1

Add Maintenance for OS X 10.10 "Yosemite"
remove DSL-change banner
Merge pull request #7688 from jawshooah/update-wd-security

Update WD Security to 2.0.0.30
Add binary stanza to Julia cask