updated history.js version to solve IE8/9 history (and exhibit) failure.

Note this is a beta version of history.js , but that seems fair trade
for getting Exhibit working again.  Watch for a final 1.8 release.

This also let me remove the previous hack I introduced to address the
problem (commit 79ff361b52643756ae4bb62ee2e0f4d144d8b0cb )
Merge pull request #15 from karger/2013-07-29_update_history

updated history.js version to solve IE8/9 history (and exhibit) failure.