[requires.io] dependency update
Merge pull request #1387 from getnikola/requires-io-master

[requires.io] dependency update on master branch
rst2html: merge source_path and l_source parameters. Fixes #1388
Rest: leave the settings._source flag alone, set _nikola_source_path instead
Merge pull request #1389 from aurelien-naldi/fix-rest-source_path

rst2html: merge source_path and l_source parameters. Fixes #1388