Update To CustomAction.cs to check the 32 bit registry on 64 bit machine...

...s.  Installing Excel 64 bit on a 64 bit machine without installing Outlook leads to no Outlook/Bitness key in the 64 bit registry - but there is one in the 32 bit registry.  For further commentary on this, see: http://stackoverflow.com/questions/2203980/detect-whether-office-2010-is-32bit-or-64bit-via-the-registry