Add a notification that undo's the update when clicked
onclick is itself an attribute function

it is not a function to add listeners for the 'onclick' event.
log the original update action to console
Group related console logs
chrome.bookmarks.update is asynchronous!!

Only log the update action and present the user with an undo
notification after the update completes though a callback.

If not then it is up to the speed with which the user clicks the
notification and race conditions whether the update is performed first
and then the rollback action or the other way round.
refactored callback argument name and log message
Visually inform user of Undo action.
refactor the creation of a timedout notification
Immediately close the update notification on click
Add function documentation
Merge pull request #6 from jeroendv/undoNotification

Undo functionality though clickable notification