testsuite: add README
testsuite: don't use whitespace in trash directory name

Use 'trash-directory.*' instead of 'trash directory.*' in directory
names for trash dirs in tests. Why have whitespace in a directory
name if you don't need it?
testsuite: allow override of SHARNESS_TEST_SRCDIR

It is useful in sub tests to override the value of SHARNESS_TEST_SRCDIR.
Don't overwrite the value if it already is set.
testsuite: Add sanity check for run_timeout functionality
testsuite: test for test_under_flux functionality

Add a slightly tricky test to ensure test_under_flux is working.
testsuite: default value for test_under_flux

Set default size for test_under_flux function to 1.
Merge pull request #42 from grondo/testsuite-fixes

testsuite fixes and minor enhancements