add sphinx/doc_readme.txt

This file explains how to generate the manual.pdf
copy pdf into main folder after compiling

the default location _build/latex/ is inconvenient...
fix package/module python weirdness

We no longer import constants in __init__ so that it works without
installing.
extract debye test, cleanup
remove unused code from seismic
Merge pull request #51 from tjhei/crazy_init_fixes

Crazy init fixes
Merge pull request #45 from tjhei/add_pdf_readme

Add pdf readme
automating setting of the equation of state
fix examples
fix user_material example