zorba-node on linux

The changes to binding.gyp and example.js were necessary so that zorba-node worked on Ubuntu with a 'standard' Zorba installation (from the Juan repos).

On Redhat, I had to make custom changes to binding.gyp that are not portable, but the change to  example.js was still required to get zorba-node to work on RedHat.  Basically the string in this line 

``` javascript
    zorba.execute("Hello from Zorba for Node"); 
```
Needed to be quoted, like this:

``` javascript
    zorba.execute("'Hello from Zorba for Node'"); 
```
I guess it must have worked on a Mac and Windows, but the test resulted in "error" on linux.  Replaced it with Zorba's own "test" as seen here http://www.zorba.io/documentation/latest/zorba/build/build_and_install#testing_install