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...
Update GitHub owner for webpage links.

That is, burnman-project->geodynamics, for GitHub links.
fix citation on homepage
add a link to geodynamics.org
Merge pull request #48 from tjhei/homepage-links

Update homepage
Manual Copy Editting

Fixed citations, added units to classes that were missing
Fixed T in isothermal bulk modulus

See title
Fixed comment on Z

Formula unit
Typo

Typo
Merge pull request #49 from lordkman/Cay_man

Manual Copy Editting
Added new VRH and HS bound benchmarks
Edited comments
Removed lovely unsquashable umlaut
Merge pull request #50 from bobmyhill/velocity_averaging

Velocity averaging
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