check if kext is present before attempting unload

this is intended to address #1941
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.
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.
Merge pull request #2034 from km2c/sqlite-browser

Add cask for SQLite Database Browser
Merge pull request #2033 from ahbeng/vlc

VLC 2.1.2
Add sha1 checksum
Change Cask for proper use of version-less download URL
Rename filename.
Rename classname.
Add Theremin
rubymine 6.0.1
Removed unnecessary uninstall
Merge pull request #2031 from mjaschen/josm

Added Cask for JOSM OpenStreetMap Editor
Merge pull request #2039 from chulkilee/rubymine-6.0.1

rubymine 6.0.1
Merge pull request #2038 from aeirola/theremin

Add Theremin
Merge pull request #2036 from hjhart/send_to_kindle

Send to kindle recipe added.