tempdir support

[stevengj]

mp.make_output_directory() now makes a temporary directory with mkdtemp.

So, you can do sim.use_output_directory(mp.make_output_directory()) to work in a temporary directory.

It would be nice to add a parameter to use_output_directory that automatically deletes the directory when the simulation destructor is called.

[oskooi]

This does not seem to be working as expected: mp.make_output_directory() creates a directory in the current directory rather than in one of the system directories (i.e. /tmp) in the way that Python's tempfile.mkdtemp does. Unfortunately the C and Python version of mkdtemp are not the same.

(As an aside, the two failing Travis tests python/tests/bend_flux.py and python/tests/mode_coeffs.py are both due to NanoComp/libctl#53 which was recently merged. The hard-coded values in the two tests likely need to be updated. cc @danielwboyce.)

[stevengj]

It now puts it in the temporary directory (/tmp or similar).

[stevengj]

I also noticed that, contrary to its name, trash_output_directory does not actually seem to "trash" anything. It just calls mkdir to create the directory, but this does not delete any existing directory.