Merge pull request #2 from duetosymmetry/master

Get rid of all your CellChangeTimes
Changes irrelevant
Merge branch 'master' of https://github.com/CyrilPitrou/xPand

Conflicts:
	Examples/4 Friedmann-Lemaitre_Perturbations.nb
MakeRule overloading removed
cleaning code
Implementation of the normal vector perturbation
Tiny tidy
Shift vector implemented
Comments added for lapse and shift
Removing extra example