Add a `--json` option to `git-list-releases` so that it can emit

the release information in JSON rather than Markdown.

Add test case for mirage#44 (repo branch listing)

bump to 0.9.2

Bump to 0.9.1

Fix OCaml version in Travis

release 0.8.6

add a opam file for pin use

tweak markdown output

Mention upload-release in READMe

Revert back to 0.8.2 (which was still unreleased)