drop help for long options if longer versions with hyphens are available
removed two superfluous parser arguments
Merged in anthon_van_der_neut/pytest/opt-drop-non-hyphened-long-options (pull request #56)

drop help for long options if longer versions with hyphens are available
changes to addoption() for hyphenated long-options
Merged in anthon_van_der_neut/pytest/opt-drop-non-hyphened-long-options (pull request #57)

changes to addoption() for hyphenated long-options
add changelog entry for anthon's hynek-fication of options,
and change the docs and tests to use the new style.
Fix issue 336: autouse fixtures in plugins work again

When an autouse fixture in a plugin was encountered None was stored as nodeid
where it used to be ''.  This broke the lookup of autouse fixtures later on.

This also adds another test for the normal fixture ordering which was slightly
wrong: a fixture without location was always added at the front of the fixture
list rather then at the end of the fixtures without location but before the
fixtures with location.
mention fix for issue 336 in changelog
fix issue317: assertion rewriter support for the is_package method
merge
refs #322: setUpClass and tearDownClass as autouse fixture and finalizer
fix issue322: tearDownClass is not run if setUpClass failed. Thanks
Mathieu Agopian for fixing.  The patch moves handling setUpClass
into a new autofixture. (XXX impl-decide if rather adding addfinalizer()
API to node's would have a similar effect)
ref #322 cleanup all teardown calling to only happen when setup succeeded.
don't use autouse fixtures for now because it would cause a proliferation
and overhead for the execution of every test.  Rather introduce a
node.addfinalizer(fin) to attach a finalizer to the respective node
and call it from node.setup() functions if the setup phase succeeded
(i.e. there is no setup function or it finished successfully)