fix tests
re-organize material and mineral base classes
fix examples
fix tests
rename minerals_base to mineral_helpers
remove composite_base, remove named_tuple, new constructor

this includes a hack that the old style constructor still works...
add debug_print() to material
update examples to new composite
update tests
Merge pull request #5 from tjhei/restructure_base_classes

Restructure base classes
add new tests
add an exception to an unfinished class
rename classes

rename Mineral, Material, Composite, EquationOfState, MGD*, SeismicData,
RadiusTable, SLB*, Seismic*
documentation fixes
rename classes in averaging_schemes
rename more classes

BM, ElasticProperties, PREM
rename mineral helper classes
Merge pull request #6 from tjhei/class_names_capital

Capitalize all classes