Time To Live Indicator for toasts

Add an optional progress bar to toasts to indicate time to live.  This is related to [Issue 188](https://github.com/CodeSeven/toastr/issues/188)
@johnpapa I just want to make sure you are aware that the variables are not options.  They are internal variables.  Do you still want them in their own object?  Or perhaps renamed more appropriately?

currentTimeOut = The total seconds before the toastr will hide itself. This will always be equal to options.timeOut or options.extendedTimeOut.

hideTime = The eta in which the toastr will be hiding itself.

progressIntervalId = The id for the setInterval which updates the progress bar width.  This is stored so that it can be cleared when the toaster is hidden.