Add the ability to change the amount of history.
Add the ability to change the amount of history.

Added code to support listening to events fired from the new select box. When a
new timeslice selection is made at the box, the appropriate amount of time will
be pulled from the history api and displayed on the page (after the current
display is wiped clean). Work towards #5.

the-hobbes/website_time_tracker,the-hobbes/website_time_tracker