added customParam constant
bugfix: native SMS invitation not working
enhancement: add support for app supplied custom parameter to be
associated to the app install.  This custom parameter will be used on
server callback to identify app install
bugfix: native SMS invitation not working when useVirtualNumber is set
to false
enhancement: add support for app supplied custom parameter to
be associated to the app install.  This custom parameter will be used on
server callback to identify app install