rework debug_print

Material.debug_print was based on a current p, T given by the last
set_state() and would return an unrolled list of minerals. This makes it
inconvenient to use and will provide the wrong information. Now it will
return a hierarchical representation independent of p,T. The old
function is now available as print_minerals_of_current_state().
update tests
Merge pull request #31 from tjhei/rework_debug_print

Rework Material.debug_print
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
include tutorials in doc, rework text

- tutorials are now included in Example doc section
- for this: "if main" needed, fix finding burnman if not installed
- Example section is somewhat work in progress
- experiment with including code directly
- include a picture as a test
doc: move examples to beginning
play with latex format
include cig title in pdf