Update to match the article.

The development now corresponds exactly to the FoSSaCS 2013 paper.
Also, the prelude is updated to the one of the master branch.
Bump Coq version.
Merge branch 'fossacs2013'

Conflicts:
	ars.v
	assertions.v
	axiomatic.v
	base.v
	doc/index.html
	expressions.v
	fin_maps.v
	memory.v
	smallstep.v
	state.v
	statements.v
	tactics.v