Update Varnish.rst

Added info of the upgrading to Varnish 4 and VCL 4.0
Added file varnish4.rst with info of the upgrading to Varnish 4 and VCL 4.0
Encode fixed
Merge pull request #115 from cleberjsantos/master

Update varnish.rst and add howto for varnish 4