Imported pyfits inside function namespace in accord with astropy conventions
Coded up abstract base class of assembly bias model, and concrete class for Satcen correlation model.

Satcen correlation model currently instantiates, but that's all. Still entirely untested.
Also, I broke vdB03 quenching model on purpose, so that will need to be fixed.
Finished debugging Satcen correlation model. Probably correct now.
Minor modification to docstring to get docs to compile
Discovered bug in destruction function. Still unfixed. Run syntax_checks.py. See new EverNote for how to fix.
Fixed bug in satellite destruction. Code now correctly handles arbitrary input functions.
Major reorganization of Assembly Bias model.

Passes the standard test of the derived mean_nsat = underlying mean_nsat, even in wildly pernicious cases.
All the same, I am not 100 percent confident. Can always revert to the previous commit, which was
uglier. Add more non-trivial tests to the test suite before moving on.
Starting to revamp make_mocks (currently broken) to accommodate new models. Also added 2-halo assembly bias ho model.
Edited docstrings.
Minor modifications to docstring
Cleaning up halo_occupation docs
Modifying equations to HOD models in halo_occupation module
Modifying documentation of Assembly_Biased_HOD_Model
--amend
Modified observables.py to make desired API clear
Modified HOD_mock so that it is no longer broken. Still super buggy.

Included new test file to make sure that a simple HOD mock can be instantiated.
Minor modifications to test suite so that silly file run_mock_instance can be deleted without consequence
Merge pull request #1 from aphearin/develop

Develop