Properly insert buffers in arrays.

Before this commit, when someone tried to insert a Buffer into an array,
the library would try to escape it (by calling the `escapeElement` on
it), which would fail because buffers don't have a `replace` method.

lib/utils.js

@@ -33,6 +33,9 @@ function arrayString(val) {
     else if(Array.isArray(val[i])) {
       result = result + arrayString(val[i]);
     }
+    else if(val[i] instanceof Buffer) {
+      result += '\\\\x' + val[i].toString('hex');
+    }
     else
     {
       result += escapeElement(prepareValue(val[i]));