fix code mistake

var in this case is hoisted to the top of the function and will blow
out any passed value for ‘e’. In order to maintain code integrity,
don’t re-var ‘e’ since it has already been declared.  Now we could
theoretically pass a value for ‘e’ and have it work correctly.
add feature to limit number of notifications

add feature to limit number of notifications that can be displayed
concurrently, and queue up the rest to be displayed when there is room.
 Add example to set max notifications to 3.
fix broken example images.
Merge branch 'master' into develop