fix: bad reference for the foreign entities
Merge branch 'master' of git://github.com/AppVentus/DataMigrationBundle

# By Thomas Beaujean (2) and Paul Andrieux (1)
# Via Paul Andrieux
* 'master' of git://github.com/AppVentus/DataMigrationBundle:
  Update usage.md
  fix typo
  add readme.md