release stage (CircleCI): Ignore untracked files

The problem was that release stage was making sure that git status
returns no output whatsoever. However, we don't care about untracked
files, so release stage should not block if there are only untracked
files in the repository.
Finished feature 75521098/release-stage-blocked-by-untracked-files.
feature finish: Handle Unicode properly

The description field was not using decode(), leading to Unicode errors
being thrown when non-ASCII characters were there.
Finished feature 75426064/unicode-error-feature-finish.
release finish: Delete tag on RB submit failure
Finished feature 75795094/make-release-finish-robust.
Bump version to 1.4.6
release finish: Roll back branches on some errors

Master and develop is not reset to the origin position when it fails to
submit the review requests or push the changes to GitHub in the end.
Finish release 1.4.6 (merge branch release/1.4.6)