tests: Adjusted test folder structure to roughly match skylines package
requirements: Replaced nosetests by py.test
tests: Fixed test_gjslint.py
tests: Fixed model tests
tests: Fixed functional tests
tests: Renamed TestTable class to ExampleTable

This was confusing the test runner
tests: Removed nose imports
setup.py: Use PyTest runner for "python setup.py test"
test_i18n: Improved test yielding and error messages
tests: Fixed flake8 issues

mostly import cleanups
tests: Added tests folder to flake8 checks
test_flake8: Run flake8 for each folder separately
requirements: Update pytest to v2.5.0
Merge pull request #216 from Turbo87/tests

Replaced nosetests by pytest