Remove obsolete authors files.
Import gitlog2changelog.py (2008-12-27)

https://github.com/cryos/avogadro/commit/8be9957e5b3b5675701ef2ed002aa9e718d4146e#scripts/gitlog2changelog.py
Issue #4: generate ChangeLog from git logs

This seems to generate long ChangeLog entries in the format we had with svn2cl,
but some commits appear to be missing.
Fixes issue #4: ChangeLog now includes single-file commits.
git-changelog: Fix list of distributed files
git-changelog: remove re.* calls for simple string matching
git-changelog: really fixes #4 (missing entries)

The script was discarding any commits which happened to include the word
'commit'.
Merge branch 'git-changelog'

Runs 'git log' on the current branch, and generates a GNU-style ChangeLog.