bugfix: move empty line filtering to after normalization
bugfix: move empty line filtering to after normalization

normalization recently added deleting of certain non-printing UTF8
characters, which means blank lines can be created by normalization,
so we have to remove them afterward instead of before (for both
train and dev, since Moses kbmira croaks on blank outputs)

thammegowda/incubator-joshua,fhieber/incubator-joshua,thammegowda/incubator-joshua,fhieber/incubator-joshua,thammegowda/incubator-joshua,fhieber/incubator-joshua,fhieber/incubator-joshua,thammegowda/incubator-joshua,fhieber/incubator-joshua,fhieber/incubator-joshua,thammegowda/incubator-joshua,thammegowda/incubator-joshua,thammegowda/incubator-joshua,fhieber/incubator-joshua,fhieber/incubator-joshua,thammegowda/incubator-joshua,fhieber/incubator-joshua,thammegowda/incubator-joshua,thammegowda/incubator-joshua