installation: use git log instead of ChangeLog
installation: use git log instead of ChangeLog

* As some other GNU GPL projects already did or think about doing,
  the detailed ChangeLog file will not be maintained in Invenio anymore,
  since `git log' plays this role perfectly well.  Therefere, recommend
  how to use `git log' instead of ChangeLog.

inveniosoftware/invenio,inveniosoftware/invenio,tiborsimko/invenio,tiborsimko/invenio