Merge pull request #20 from cider-team-mercury/latex_materials

Updated liquidus models to be consistent with the Anzellini melting curve. Improved figures.
Improved generation of figures for comparing temperature slopes
Merge branch 'master' of https://github.com/cider-team-mercury/mercury into latex_materials
 Fixed mistake in reporting average heat capacities in build_planet, recalculated values on the 'wishlist', generated figures of the clapeyron slope