DOC: SyntaxError in pd.read_msgpack examples
`In [319]: for o in pd.read_msgpack('foo.msg',iterator=True):`
`   .....:     print o`
`   .....: `
`  File "<ipython-input-319-a0f40395739e>", line 2`
`    print o`
`              ^`
`SyntaxError: Missing parentheses in call to 'print'`
