CHANGELOG.md: add unpublished Shaarli Community releases

Relates to https://github.com/shaarli/Shaarli/issues/663
See http://keepachangelog.com/en/0.3.0/

These entries correspond to the first lightweight tags present on the
Shaarli Community repository. As there are no corresponding release (notes),
the changelog is based on relevant elements from the Git commit log.

Signed-off-by: VirtualTam <virtualtam@flibidi.net>