Switch to using print function (for Python 3) using 2to3
Switch to using print function (for Python 3) using 2to3

Updated main code using the 2to3 print fixer:

$ 2to3 -w -n --no-diffs -f print graphs.py
RefactoringTool: Refactored graphs.py
RefactoringTool: Files that were modified:
RefactoringTool: graphs.py

Also updated the docstrings the same way:

$ 2to3 -w -n --no-diffs -f print -d graphs.py
RefactoringTool: Refactored graphs.py
RefactoringTool: Files that were modified:
RefactoringTool: graphs.py

Manually added the future import line so we can use the
print function under Python 2.6 and 2.7 as well.

peterjc/ccn