Updated barrel cortex example for new clock system
Suppress some resolution warnings in the tests
Reduce the number of resolution conflict warnings. Closes #310
Mark tests that do not require codegen as codegen-independent (replacing the `SkipTest` approach) and test them (together with the doctests) separately from the other tests.
Skip some long-running tests by default
Merge pull request #331 from brian-team/pass_down_user_code

Reduce the number of resolution conflict warnings
Add scripts to run the long test suite for individual codegen targets
Add scripts to run the long test suite for individual codegen targets
[ci skip]
Document the test attributes in the developer docs
[ci skip]
Merge remote-tracking branch 'origin/master' into cython_codegen2

Conflicts:
	brian2/tests/test_neurongroup.py
Merge pull request #326 from brian-team/cython_codegen2

Cython support
Merge branch 'master' into openmp

Conflicts:
	brian2/tests/__init__.py