travis: don't test node v0.6 or v0.8
travis: don't test node v0.6 or v0.8

Browserify won't install cause it uses the ^ syntax :\

Most likely though, the tests will still continue to pass for those
versions for the foreseeable future...

vladimir-kotikov/plist.js,TooTallNate/plist.js,Jonahss/plist.js