move test file below their module

So test for nextbiopy/*.py will be at nextbiopy/test/test_*.py
            nextbiopy/io/*.py  ---->  nextbiopy/io/test/test_*.py
All test can still be perform by

    $ python3 setup.py test
or  $ nosetests-3.3

For testing particular file, use

    $ nosetests-3.3 nextbiopy.test.test_core
line python official doc to version 3.x
use clearer title
add reference anchor of title
finish doc for testing guideline