relax constraint on stog for stog-rdf: < 0.14
add stog-writing 0.13.0
add xmldiff 0.4.0
git pushMerge branch 'master' of
https://github.com/OCamlPro/opam-repository
tighter constraint on rss for stog 0.4 -> 0.7
Merge branch 'master' of https://github.com/OCamlPro/opam-repository
Merge pull request #2846 from zoggy/master

add stog-writing 0.13.0 and xmldiff 0.4.0