Repackage so hl7parser can be installed with pip or easy_install.

Moved everything into an hl7parser package,
for backward compatibility existing code can:
    import hl7parser as hl7

unittests and doctests can be run with:
    python setup.py test
Merge pull request #4 from rectalogic/packaging

Repackage so hl7parser can be installed with pip or easy_install.