Fix for Node 0.8 thru 0.10

Author: Logikgate

lib/linux.js

@@ -1,7 +1,7 @@
 var execFile = require('child_process').execFile;
 
 module.exports = function (iface, callback) {
-    execFile("cat", ["/sys/class/net/", iface, "/address"], function (err, out) {
+    execFile("cat", ["/sys/class/net/" + iface + "/address"], function (err, out) {
         if (err) {
             callback(err, null);
             return;