Add initial versions of tutorials
Work on tutorials
Edits
Add a bunch of text for step_1
Add lots of text, modifications for step_2
Text for step_3
Adjustments, text
minor text changes

changed 'mantle' to 'lower mantle'
and added formula for stishovite and wuestite
% to Fraction in figure label
More text
Don't need to return mineral.
Split up onto two lines
Merge pull request #34 from ian-r-rose/cider_tutorials

Cider tutorials
Initial working copy (non-functional) adding solid solutions
Adding non-functional solidsolution.py
Abbreviate kd
Add Modified Tait EoS and expression for G
Added molar mass calculator and data table
Minor corrections
Added endmember Gibbs with Landau, and a new test script.