TST: Always try to close file descriptors of tempfiles

TST: Close file descriptors in io/tests/pytables
Merge pull request #5626 from jtratner/always-close-tempfiles

TST: Always try to close file descriptors of tempfiles
BUG/TST: importing util.clipboard shouldnt print to stdout (nosetests)
Merge pull request #5627 from y-p/PR_no_noise_clipboard

BUG/TST: importing util.clipboard shouldnt print to stdout (nosetests)
ENH: Make set_option into a contextmanager that undos itself on __exit__