make note of when process.versions.modules became visible

lib/binary_name.js

@@ -12,6 +12,8 @@ var Binary = function(options) {
   this.platform = options.platform || process.platform;
   this.target_arch = options.target_arch || process.arch;
   if (process.versions.modules) {
+    // added in >= v0.10.4 and v0.11.7
+    // https://github.com/joyent/node/commit/ccabd4a6fa8a6eb79d29bc3bbe9fe2b6531c2d8e
     this.node_abi = 'node-v' + (+process.versions.modules);
   } else {
     this.node_abi = 'v8-' + process.versions.v8.split('.').slice(0,2).join('.');