Fixed warnings: 1_6.W001 and RemovedInDjango18Warning
Added python 3 support for travis-ci (and let them fail for now).

test_test (test_project.test_app.tests.TestTestApp) ... /Volumes/Shared HD/Developing/py/django-interval-field/test_project/test_app/views.py:8: RemovedInDjango18Warning: Creating a ModelForm without either the 'fields' attribute or the 'exclude' attribute is deprecated - form TestForm needs updating

?: (1_6.W001) Some project unittests may not execute as expected.
	HINT: Django 1.6 introduced a new default test runner. It looks like this project was generated using Django 1.5 or earlier. You should ensure your tests are all running & behaving as expected. See https://docs.djangoproject.com/en/dev/releases/1.6/#new-test-runner for more information.
Added python 3 support (hopefully)
Fix: "DeprecationWarning: Please use assertEqual instead".
Rewrite of test_project + real test for this app.
This ensures python3 compatibility and shows better how 'interval' works.

Some improvements towards python 3 support have also been made.
Fix relative import bug and silence Deprecation Warnings.
Code cleanup
TravisCI will now run all tests using its PostgreSQL backend.
Drop "allowed failures" for python 3.

Fix hardcode issues in the tests
Added German translations.
Merge pull request #4 from Matt3o12/master

Python 3 support, rework of the test app, german translations, by @Matt3o12