Merge branch 'release/0.9.4' into develop
version bump to 0.9.5a1.dev1
adds next entry in history
limit django-polymorphic version to 0.4.0, since 0.4.2 seems to break with django-mptt
updates testsuite to use django-1.3 compatible version of django_polymorphic. don't enforce old version for everybody.
Fix error raising in FILER_DEBUG mode

Re-raising the error modify the trackback and make it hard to debug.
Just calling raise in a except statement re-raise the error with
its full traceback, making it easier to debug.