Use print() function to fix install on python 3

clint 0.3.2 can't be installed on python 3.3 because of this print statement.

```
Downloading/unpacking clint
  Running setup.py egg_info for package clint
    Traceback (most recent call last):
      File "<string>", line 16, in <module>
      File "/home/simon/lib/virtualenvs/clint/build/clint/setup.py", line 12, in <module>
        import clint
      File "./clint/__init__.py", line 22, in <module>
        from . import textui
      File "./clint/textui/__init__.py", line 17, in <module>
        from . import prompt
      File "./clint/textui/prompt.py", line 33
        print prompt
                   ^
    SyntaxError: invalid syntax
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):

  File "<string>", line 16, in <module>

  File "/home/simon/lib/virtualenvs/clint/build/clint/setup.py", line 12, in <module>

    import clint

  File "./clint/__init__.py", line 22, in <module>

    from . import textui

  File "./clint/textui/__init__.py", line 17, in <module>

    from . import prompt

  File "./clint/textui/prompt.py", line 33

    print prompt

               ^

SyntaxError: invalid syntax

```