Update requirements

Flask==0.10.1
SQLAlchemy==0.8.1
celery==3.0.19
nose==1.3.0
psycopg2==2.5
numpy==1.7.1
alembic==0.5.0
Add unit tests for import_coverage task

Implemented with some fixtures using the fixture package which
unfortunately needs some monkey patching for now (see the top of
tests/fixtures.py).