v0.006

  [Changes]
  - Rename 'git gerrit backout' to 'git gerrit upstream', which is
    more meaningful.

  - The git-gerrit.username config variable doesn't exist anymore. The
    username can be informed via the git-gerrit.baseurl variable.

  - Improved documentation.

  [New features]
  - Now 'git gerrit co' is an alias for 'git gerrit checkout'.

  - Now 'git gerrit up' is an alias for 'git gerrit upstream'.

  - You can force 'git gerrit upstream' to delete a new change-branch
    with the --delete option.