Python 3 compatibility

[joshgachnang]

Various things, such as print being a function in 3, should be mentioned and used when possible in the book. Python 2.7 supports many of Python 3's features, and the book should be written to make the transition easier. Update all the print statements, ensure sorted() vs .sort, etc.

[joshgachnang]

As mentioned in another issue, the book should also exclusively use the new string formatting.

[CrazyPython]

List of updates: print() .format() urllib.urlopen is now urllib2.urlopen() integer division from __ future __ import ?UPDATE?

[CrazyPython]

Add more to the list then delete your comment once I added it.