Switch to more consistent Quad4::volume() implementation.
Switch to more consistent Quad4::volume() implementation.

This now looks more like the other Elem::volume() specializations.

90jrong/libmesh,balborian/libmesh,roystgnr/libmesh,pbauman/libmesh,benkirk/libmesh,balborian/libmesh,BalticPinguin/libmesh,svallaghe/libmesh,BalticPinguin/libmesh,friedmud/libmesh,libMesh/libmesh,dschwen/libmesh,svallaghe/libmesh,dschwen/libmesh,coreymbryant/libmesh,giorgiobornia/libmesh,pbauman/libmesh,vikramvgarg/libmesh,jwpeterson/libmesh,dschwen/libmesh,jwpeterson/libmesh,pbauman/libmesh,BalticPinguin/libmesh,balborian/libmesh,libMesh/libmesh,svallaghe/libmesh,capitalaslash/libmesh,libMesh/libmesh,dschwen/libmesh,hrittich/libmesh,balborian/libmesh,hrittich/libmesh,capitalaslash/libmesh,coreymbryant/libmesh,libMesh/libmesh,friedmud/libmesh,dschwen/libmesh,benkirk/libmesh,libMesh/libmesh,giorgiobornia/libmesh,capitalaslash/libmesh,capitalaslash/libmesh,coreymbryant/libmesh,BalticPinguin/libmesh,jwpeterson/libmesh,giorgiobornia/libmesh,pbauman/libmesh,jwpeterson/libmesh,benkirk/libmesh,vikramvgarg/libmesh,pbauman/libmesh,roystgnr/libmesh,roystgnr/libmesh,jwpeterson/libmesh,aeslaughter/libmesh,BalticPinguin/libmesh,capitalaslash/libmesh,friedmud/libmesh,giorgiobornia/libmesh,jwpeterson/libmesh,vikramvgarg/libmesh,hrittich/libmesh,benkirk/libmesh,hrittich/libmesh,libMesh/libmesh,svallaghe/libmesh,benkirk/libmesh,svallaghe/libmesh,hrittich/libmesh,roystgnr/libmesh,vikramvgarg/libmesh,dschwen/libmesh,benkirk/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,giorgiobornia/libmesh,capitalaslash/libmesh,friedmud/libmesh,aeslaughter/libmesh,90jrong/libmesh,balborian/libmesh,friedmud/libmesh,90jrong/libmesh,libMesh/libmesh,libMesh/libmesh,capitalaslash/libmesh,90jrong/libmesh,vikramvgarg/libmesh,jwpeterson/libmesh,hrittich/libmesh,roystgnr/libmesh,dschwen/libmesh,coreymbryant/libmesh,svallaghe/libmesh,svallaghe/libmesh,aeslaughter/libmesh,friedmud/libmesh,friedmud/libmesh,pbauman/libmesh,giorgiobornia/libmesh,giorgiobornia/libmesh,aeslaughter/libmesh,hrittich/libmesh,benkirk/libmesh,aeslaughter/libmesh,dschwen/libmesh,90jrong/libmesh,friedmud/libmesh,BalticPinguin/libmesh,vikramvgarg/libmesh,pbauman/libmesh,balborian/libmesh,friedmud/libmesh,balborian/libmesh,aeslaughter/libmesh,coreymbryant/libmesh,vikramvgarg/libmesh,balborian/libmesh,giorgiobornia/libmesh,90jrong/libmesh,svallaghe/libmesh,pbauman/libmesh,coreymbryant/libmesh,coreymbryant/libmesh,roystgnr/libmesh,capitalaslash/libmesh,BalticPinguin/libmesh,roystgnr/libmesh,balborian/libmesh,aeslaughter/libmesh,aeslaughter/libmesh,roystgnr/libmesh,hrittich/libmesh,balborian/libmesh,90jrong/libmesh,hrittich/libmesh,aeslaughter/libmesh,giorgiobornia/libmesh,90jrong/libmesh,coreymbryant/libmesh,svallaghe/libmesh,90jrong/libmesh,benkirk/libmesh,vikramvgarg/libmesh,benkirk/libmesh,pbauman/libmesh,vikramvgarg/libmesh