Fix insertion of some characters in iText

When typing periods, commas, opening parentheses, ampersands, percents and quite possibly other characters in iText, they are not inserted. Bug happening on OS X and Windows.

It's the same bug as #1573 but another solution since event.charCode used in that pull-request is deprecated (https://developer.mozilla.org/en-US/docs/Web/API/event.charCode).

The fix here is the removal of the `e.keyCode in this._keysMap` check from the keypress callback. There seems to be no side-effect.