Update node-guardtime to use node-gyp

We've updated node-guardtime to use node-gyp which now does the following:
    * removes all waf and other build scripts
    * compiles gtbase, gthttp, and gtpng as static libraries
    * uses 'bindings' module for ease of use for including timesignature.node in guardtime.js
    * updated package.json

These updates still require you to compile node to use a shared openssl as guardtime (timesignature) uses symbols not available when using a statically compiled node.