Computation of the magnetoelectric responses

Implemented Leung-Prodan formula to model and classify the disordered
3D Fu-Kane-Mele model in EMV6.f90.  Computed the energy gap of the
model in EMVGap.f90.

MEresponse.pdf shows the numerical results for various disorder
simutlations.
Merge branch 'master' of https://github.com/bryleung/Magnetoelectric-Responses-Formula
Revert "Computation of the magnetoelectric responses"

This reverts commit f244bb44bd9495419e2ae7d6ff453ee095ca059b.