Pyptex

* Quick Windows support modification (commit 11ae6a1 by Sebastien Loisel)

* documentation tweaks (commit 089850c by Sebastien Loisel)

* documentation tweaks (commit c790b78 by Sebastien Loisel)
* documentation fixes (commit 5fbd704 by Sebastien Loisel)

* Added pyp.clear and pyp.freeze. Also, recent sympy broke latex printing in some cases, fixed it. (commit 167d145 by Sebastien Loisel)
* Create CODE_OF_CONDUCT.md (commit 9a02827 by Sébastien Loisel)
* Create pull_request_template.md (commit 5905350 by Sébastien Loisel)
* Update issue templates (commit 14d75cc by Sébastien Loisel)
* Create contributing.md (commit 0829eff by Sébastien Loisel)

* documentation tweak and make tweak. (commit c911ab0 by Sébastien Loisel)
* tweaked building of scripts/pyptex to avoid inadvertantly causing a rebuild when using make (commit 10827b8 by Sébastien Loisel)

* Work around pip shebang bugs in a less brittle way by generating the pyptex script from setup.py. (commit 7daa386 by Sébastien Loisel)