Documentation: Update required Git version to 1.7.2
Documentation: Update required Git version to 1.7.2

Our 'git-gitlab-push' script requires Git 1.7.2 or greater to use the
'git -c <name>=<value> ...' configuration option.  Since 1.7.2 came out
in 2010 it is reasonable to expect developers to have it in 2015.

SimVascular/VTK,sumedhasingla/VTK,jmerkow/VTK,candy7393/VTK,candy7393/VTK,msmolens/VTK,gram526/VTK,mspark93/VTK,demarle/VTK,keithroe/vtkoptix,sumedhasingla/VTK,sankhesh/VTK,msmolens/VTK,mspark93/VTK,SimVascular/VTK,demarle/VTK,sumedhasingla/VTK,jmerkow/VTK,SimVascular/VTK,mspark93/VTK,gram526/VTK,sankhesh/VTK,gram526/VTK,msmolens/VTK,SimVascular/VTK,SimVascular/VTK,mspark93/VTK,demarle/VTK,jmerkow/VTK,jmerkow/VTK,gram526/VTK,mspark93/VTK,candy7393/VTK,candy7393/VTK,keithroe/vtkoptix,candy7393/VTK,gram526/VTK,sankhesh/VTK,jmerkow/VTK,keithroe/vtkoptix,SimVascular/VTK,mspark93/VTK,gram526/VTK,jmerkow/VTK,candy7393/VTK,sumedhasingla/VTK,sumedhasingla/VTK,msmolens/VTK,sumedhasingla/VTK,msmolens/VTK,SimVascular/VTK,msmolens/VTK,demarle/VTK,gram526/VTK,SimVascular/VTK,sumedhasingla/VTK,sankhesh/VTK,candy7393/VTK,msmolens/VTK,sankhesh/VTK,gram526/VTK,candy7393/VTK,sankhesh/VTK,msmolens/VTK,demarle/VTK,mspark93/VTK,demarle/VTK,jmerkow/VTK,sankhesh/VTK,sumedhasingla/VTK,keithroe/vtkoptix,keithroe/vtkoptix,jmerkow/VTK,keithroe/vtkoptix,mspark93/VTK,keithroe/vtkoptix,sankhesh/VTK,demarle/VTK,keithroe/vtkoptix,demarle/VTK