Remove tox.ini.

Tox has been unstable at best since various changes in virtualenv and
pip so I've abandoned its usage for the time being.  My public builds
run through Travis CI so I get the 2.7 + 3.3 coverage there.
README: Add development environment section.
Makefile: Add a basic makefile.
Makefile: Add housekeeping targets.
Makefile: Add test target.
Makefile: Add lint target.
Makefile: Add sdist target.
Makefile: Add docs target.
README: Fix formatting error.
Merge branch 'feature/rework-build-environment' into develop