update the documentation to refere to GnuPG v2 instead of latest GnuPG

The latest GnuGP tool (https://gnupg.org/download/)  is now storing keyring in a new format file 'kbx' instead of 'gpg' which make the current documentation incomplete for a new user. The propose pull request consists of adding documentation to explain how to generate a gpg using the latest GnuGP tool

Add helm-hashtag plugin

adding Helmsman in docs/related.md

https://github.com/balboah/helm-hashtag

fix occurences typo in charts.md

Create missing directories when saving files in chartutil.SaveDir

remove deprecated -e flag to `docker login`

fix(helm): update helm reset --force tip for clarity

fix(circle): fix download link to download.docker.com

Docker stopped releasing binaries to get.docker.com as of 17.03.0-ce. They are all hosted at download.docker.com now.

I also had to downgrade docker to 17.09.0-ce because that's the only version that both download.docker.com and
CircleCI support.

https://download.docker.com/linux/static/stable/x86_64/
https://circleci.com/docs/2.0/building-docker-images/#docker-version

refactor prettyError, closes #3381

Reduce binary size

Fix typo

bump docker to 17.11.0-ce

defer in loop may cause resource leak

fix the implicit dependency of TestSetAppVersion test on previous tests

Minor documentation fixes

* add test for rolling back from a FAILED deployment

* Update naming of release variables

Use same naming as the rest of the file.

* Update rollback test

- Add logging
- Verify other release names not changed

* fix(tiller): Supersede multiple deployments

There are cases when multiple revisions of a release has been
marked with DEPLOYED status. This makes sure any previous deployment
will be set to SUPERSEDED when doing rollbacks.

Closes #2941 #3513 #3275

Fix linting bug with charts containing more than one hyphen

Fix the output leak to stdout during build by tests under pkg/releasetesting

Mute upgrade --install default namespace warning

fix the output leak from test code under pkg/tiller

Fix minor typo

Clean up temporary "helm-repotest-*" directories left behind by tests under cmd/helm

Fix link to Slack

docs: Fix FromJson comment

Bump client side grpc max msg size

docs(helm): Added kubeVersion to documentation.

docs(helm): Added kubeVersion to documentation and examples.
Adjusted wording for the Chart.kubeVersion description
Removing redundant wording for Chart.kubeVersion description

use an underscore for release_checklist.md

Support installing plugins by relative path

```
helm plugins install .
```

Newer gits don't like checking out an empty string.

```
empty string is not a valid pathspec. please use . instead if you meant to match all paths
```

Tiller should only enforce what we expect from Helm

update docs to demonstrate best practices in regards to named templates