The library by Mario H. is the one that's published in the Arduino Playground. On several sites where I2C LCD's are sold, you can also download a library but 9 out of 10 they are the DFRobot library.
You still haven't bothered to post a link (HTML Links Hyperlinks).
You asked about which lead is the emitter on the transistor.
There were several references to the wiring of the transistor posted before I asked this rhetorical question (Rhetorical question - Wikipedia). If you really comprehended what was going on you would have pointed your response toward a more appropriate party.
Don