bump version to 3.1.6 in line with rml2pdf
bump version to 3.1.6 in line with rml2pdf

Distrotech/reportlab,kanarelo/reportlab,kanarelo/reportlab,Distrotech/reportlab,kanarelo/reportlab,kanarelo/reportlab,Distrotech/reportlab,Distrotech/reportlab,Distrotech/reportlab,kanarelo/reportlab