check if kext is present before attempting unload

this is intended to address #1941
document caveats, after_install, after_uninstall

in FAQ.md and CONTRIBUTING.md.  Also divide fields in CONTRIBUTING.md
into two sections: frequently-used and infrequently-used .
refine & document order of uninstall keys

Proposed order - :script, :launchctl, :quit, :kext, :pkgutil, :files.  Quit
a process before attempting to unload an assocated kext, unload kext before
attempting to delete the associated file, etc.  Arguably :script fits
loically with :files near the end of the list.  However, we also have
:after_uninstall which implicitly fires immediately after :files.
Therefore, running :script early provides greater functionality.
add uninstall stanza for pckeyboardhack.rb
safer test for currently running app

The previous version could fail if the specified bundle was not installed.
Here we tell "System Events" until determining it is safe to do otherwise.
Merge pull request #2023 from rolandwalker/doc_more_fields

document caveats, after_install, after_uninstall
Upgrade Vagrant to 1.4.0

http://www.vagrantup.com/downloads.html
http://www.vagrantup.com/blog/vagrant-1-4.html
Merge pull request #2024 from rolandwalker/uninstall_order

refine & document order of uninstall keys
changelog nitpicks

now that @rolandwalker is an official contributor we don't need to call
him out on every change; he gets infinite `<3`s :)
add uninstall stanza to noejectdelay.rb
add uninstall stanza to xquartz.rb
Merge pull request #2028 from rolandwalker/noejectdelay_uninstall

add uninstall stanza to noejectdelay.rb
Merge pull request #2030 from rolandwalker/uninstall_xquartz

add uninstall stanza to xquartz.rb
Merge pull request #2027 from fsargent/patch-2

Upgrade Vagrant to 1.4.0
Merge pull request #2025 from rolandwalker/pckeyboardhack_uninstall

add uninstall stanza for pckeyboardhack.rb
Added Cask for JOSM OpenStreetMap Editor
VLC 2.1.2
Add cask for SQLite Database Browser

Cask installation for SQLite Database Browser
sqlitebrowser.sourceforge.net/
Add Mpeg Streamclip cask

Cask installationfor MPEG Streamclip http://www.squared5.com/
Send to kindle recipe added.