Added check for "exhibit-dev" argument.  Putting "?exhibit-dev=true"
on the url of the page containing the exhibit will force exhibit to
load the unbundled (and unminified) code for easier debugging, as well
as turn off history.
Merge pull request #20 from karger/2013-08-05_exhibit_dev_flag

Added debugging url parameter.  Putting "?exhibit-dev=true"