Added logical AND, OR and XOR methods

Added `logicalAND`, `logicalOR` and `logicalXOR` methods to the `Image` class.

#### To test
```
display = new Display(".livePreview")
size = display.resolution()

console.log size

i1 = $("<img/>").attr("src", "images/kitty.jpg").get(0)
i1 = new CVImage(i1)
i1 = i1.resize(320, 240)

i2 = $("<img/>").attr("src", "images/lenna.png").get(0)
i2 = new CVImage(i2)
i2 = i2.resize(320, 240)

# Now run logical method like so
# i3 = i1.logicalXOR(i2)
# i3.show display
```