Python 3 incompatible

[louwersj]

It looks like some parts of the code are not able to work with the latest releases of Python.

below code is used in rake.py
sorted_keywords = sorted(keyword_candidates.iteritems(), key=operator.itemgetter(1), reverse=True)

However, iteritems() is no longer supported in python 3, this makes that the code cannot be used in the latest releases of Python.

[louwersj]

To ensure it will work with python 3 you will need to write the line as shown in the example below:

sorted_keywords = sorted(iter(keyword_candidates.items()), key=operator.itemgetter(1), reverse=True)

[sfischer13]

#11 should fix this.