chore($sniffer): Remove $sniffer.hashchange

The hashchange event is not supported only in ancient browsers like Android<2.2
and IE<8. Angular never really supported IE7 and in 1.3 where support for IE8
is dropped it makes even less sense to check for hashchange support.
chore($sniffer): Remove remnants of separate documentMode handling

Since msie is now set to document.documentMode, it's not necessary to keep
the documentMode in a separate property.