Merge branch 'devel'
Use absolute rather than relative "up-the-ladder" imports.

This eases the problem of running the unittests via the command line
with "python -m unittest discover -s /start/path".  #53
Refactored configuration tests into new file.
Moved configuration file parsing back to lib.openjp2
Added runtests function to discover and run tests from within python.
Updated docs to reflect running tests from within python.
Merge branch 'issue53' into devel