Use TextTestRunner instead of unittest.main()

The 'exit' parameter of unittest.main(), which, when set to False,
displays the result on standard output without calling sys.exit(), was
not added until Python 2.7, but we need our code to be 2.6 compatible.
TestLoader and TextTestRunner do not suffer from this problem, and are
in fact a preferable way to run the tests, since they give us a much
finer level of control.
Install libjpeg62 — required by SCAMP

This fixes the error "while loading shared libraries: libjpeg.so.62:
cannot open shared object file: No such file or directory" when SCAMP
is run on the Travis CI virtual machine.
Make a symbolic link between libplplotd.so.9 and libplplotd.so.11

SCAMP requires libplplotd.so.9, but Ubuntu 12.04 comes with version 11
of PLplot. This is admittedly an inelegant workaround, but we can fix
the error "while loading shared libraries: libplplotd.so.9: cannot
open shared object file: No such file or directory" by creating a
symbolic link between libplplotd.so.9 and libplplotd.so.11, as
suggested by Emmanuel Bertin himself.

AstrOmatic Forum - SCAMP and PLPLOT:
http://www.astromatic.net/forum/showthread.php?tid=823