Rejigged SolidSolution class
Added check for endmember and solid solution member compositional equality
Documented and changed name of sample_pressure (now eos_pressure)
Changed comment blob for burnman.SolidSolution
Add pressure to the various EOSs that need it
Initial version of SolutionModel class, including one that does nothing, and IdealSolution class, a SymmetricVanLaar class, and an AsymmetricVanLaar class.  Still work to be done

Conflicts:
	burnman/minerals/HP_2011_ds62.py
Add missing file
Rename classes

Conflicts:
	burnman/minerals/HP_2011_ds62.py
	burnman/minerals/SLB_2011_w_solid_solutions.py
Commented functions in processchemistry.py
Patch up so that the new stuff works as a package

Conflicts:
	burnman/minerals/SLB_2011_w_solid_solutions.py
Bug fixes
Move out of burnman directory
Add the enthalpy of solution benchmark
Added compositional array construction
Split configurational entropy from ideal gibbs
Minor bug fix
Fix typos
Start trying to do configurational entropy benchmark
Bugfix
Reproduce two of the curves from fig 3b