Transitive dependency to GPLv3 package findhit-util

Hi, we're looking to use this lib in a commercial project, and whilst checking the licenses noticed that node-smpp depends on `findhit-proxywrap` (BSD) which depends on `findhit-util` (GPLv3), meaning any derivative works need to be GPLv3 as well.

I've opened cusspvz/proxywrap#36 to see about removing that dep, but if that's not possible would you be open to a PR switching to a fork that removes the GPLv3 dep?