Provision to have custom name for mailclasses
Removed BaseTestCase from __init__.py.
BaseTestCase is needed to workout faulty inheritance.
Changed the endicia readonly test. - assertRaises has been
parameterized.
test_carrier and test_stock added and refactored to increase coverage.
Fixed test_endicia after pull and rebase on upstream.
Added endicia >= 0.5 requirement to setup.py.
Merge pull request #53 from VaticanCameos/endicia-test

Tests for readonly nature of endicia-mailclass.
Integration with trytond-shipping #5974