build: Increment version to 0.13.4
build: Increment version to 0.13.4

GNOME/libgdata,Pecisk/libgdata,Pecisk/libgdata,Distrotech/libgdata,pwithnall/libgdata,Distrotech/libgdata,Pecisk/libgdata-gtasks,Pecisk/libgdata,pwithnall/libgdata,Pecisk/libgdata-gtasks,Pecisk/libgdata-gtasks,Distrotech/libgdata