Add parentheses to a print statement so it compiles under Python 3
Just fixing a Python 2-style print statement in docs/make.py so it'll compile under Python 3. (Untested but I can't imagine how this would break anything)

Thanks, @diazona .

In case anyone reviewing this isn't aware, Python 2 treats this as a print statement with a single bracketed expression, so it won't change anything there.
 I'll merge this in. But there's basically no chance the docs will build on Python 3 because it has to process the output/figures in the code examples in the docs using sphinxext/ipython_directive.py.
 OK, thanks. I hadn't gotten a chance to test the patch so I wasn't sure if that was the only thing holding up the compilation on Python 3 or not.
