allow runtests.py to run only certain tests
allow runtests.py to run only certain tests

Example:
$ python runtests.py -local matrices linalg

upiterbarg/mpmath,upiterbarg/mpmath,Alwnikrotikz/mpmath,thegooglecodearchive/mpmath,tectronics/mpmath,tectronics/mpmath,thegooglecodearchive/mpmath,Alwnikrotikz/mpmath