fix(ie8): recognise event.which in keyboard events

IE8 does not support event.which by default, breaking several keyboard functionalities such as expanding dropdowns using the down arrow key.

Normalised charCode, keyCode into event.which if it's not already present.
chore(packageJson): ref fork instead of original

Properties referenced angular-ui/bootstrap; for clarity that we're working on a fork have updated to BeyondD/bootstrap.