Removed pip installs from Makefile + serve docs

view-docs now starts a server for the docs.
Upload to PyPI using twine, as recommend by
https://packaging.python.org/en/latest/
Fix file names in MANIFEST.in and setup.py

Added keywords to setup.py metadata as well.
Initial devel docs. Checklist for making releases
Added version number and release date to changelog
Clean everything n rebuild packages before upload

Be specific about it on the docs. versioneer might make packages with
the wrong version if it is not repackaged
Make upload doesn't work

Twine needs to be given the PyPI password through the command-line.
Simpler to run it separately since the command is pretty easy.
Started new section on the changelog
Pull requests section in developer docs

A guide for PRs including the checklist and some other information.
Starts to tackle #25
Merge branch 'master' into tesseroid-kernels

Conflicts:
	doc/changelog.rst