Clean up integrator tests.
Clean up integrator tests.

* Remove unused imports
* Make test class *not* a subclass of TestCase and rename it so nose sees it
* Only build the default solver in TestSolver.setUp and also add tearDown
* Change time range in TestSolver so it actually triggers jacobian evaluation
* Clean up docstrings
* Change to numpy.allclose for comparing numeric results to be more explicit
  about what's being done
* Add vode + analytic_jacobian test
* Drop analytic_jacobian from earm and robertson general simulation tests as
  generating the jacobian is very slow.

alubbock/pysb,johnbachman/pysb,jmuhlich/pysb,pysb/pysb,LoLab-VU/pysb,johnbachman/pysb,LoLab-VU/pysb