Examples syntax (avoid errors installing on Python 3)

[takluyver]

Installing on Python 3 attempts to byte-compile the example files for some reason (#1470), mostly just choking on print statements. This just updates the print statements. It doesn't get rid of all the errors, but it's half a dozen, rather than filling up the terminal with errors. The remainder are harder to clear up without adding an abstraction layer, which runs counter to the point of examples.

For a single argument, the brackets don't make any difference on Python 2: print(x) will work exactly like print x. Where it's called with multiple arguments, I've put from __future__ import print_function at the top of the file.

I also spotted a couple of lingering references to ipclusterz, which was the name of the new ipcluster before we dropped the old parallel framework, so I cleaned them up.

[fperez]

Great, thanks for doing this. I was pretty annoyed by that flood of errors last night when testing on py3, so I'm glad you went through this effort. Merging now.