Added functions for computing gravitational energy in two ways in build_planet
added functions for detecting iron snow regime. Unfortunately it looks like something is messed up with our material modesl because I am finding iron snow to be predicted in all cases
Added tests to mercury_minerals.py found inconsistencies in iron parameters from Hauck 2010, going to replace with material properties cited by Dumberry 2014 which are better suited for this pressure range.
Changed material data to those referenced by dumbarry and included an 'extrapolated' model for a higher S concentration end-member that reproduces the expected density curve @ 10 wt %
Cleaning up stuff that was not being used in mercury_minerals
Rearranged code such that mercuryModel is a daughter of coreModel, but have not yet debugged. Added mantel mineralogy and core partitioning to mercury_reference.py
finished debugging for restructured mercuryModel class
Merge pull request #11 from cider-team-mercury/gravitational_energy

Gravitational energy