move docs around

CONTRIBUTING.md

ProofMode.md

README.md

docs/editor.md

docs/heap_lang.md

docs/proof_guide.md

docs/proof_mode.md

docs/style_guide.md

tex/.gitignore

tex/algebra.tex

tex/base-logic.tex

tex/bib.bib

tex/constructions.tex

tex/derived.tex

tex/extended-logic.tex

tex/iris.sty

tex/iris.tex

tex/language.tex

tex/listproc.sty

tex/locallabel.sty