docs(chart_template_guide): remove discussion of blocks

First alias would be dependency rename

Allow updating chart dependencies when packaging a chart

There are a lot of weird edge cases when using blocks inside of charts,
and we have been telling users to avoid using them for the last six
months. This just removes the documentation about them. It also adds a
warning about why blocks should not be used.

fix(helm): Ensures tiller pod lands on a linux node

fix(tiller): make GetReleaseContent return any release

fix(helm): remove unnecessary values merge in processImportValues

Without a node selector to ensure that tiller deploys on a linux node,
the tiller pod can have issues starting in a mixed cluster.

Fixes #2420

fix(helm): modify `helm repo update` help info

The former help info may cause misunderstanding that this command
can update content of charts existing in remote respositories while
it does pull charts' info from remote repositories.

This trivial modification leads better understanding.

Added -u flag that would cause helm dep up before running helm package

Fixes https://github.com/kubernetes/helm/issues/2128

```
- name: <dependency-chart-name>
  alias: <alias-name-to-be-used>
  version: <dependency-chart-version>
  repository: <dependency-chart-version>
```

Fixes https://github.com/kubernetes/helm/issues/2508

For some reason, GetReleaseContent was configured to return the latest
release only if it is in state DEPLOYED. But a release with a version is
returned regardless of release. This made it really hard to debug failed
releases, even though we have the data to show.

Closes #2525

fix(helm): fix race conditions in flag parsing

fix(helm): prepend repo URL to packages missing scheme

fix(2452): sort templates before parse

docs(helm): fix typo

adjust the check parameter order for uninstall 

fix(docs): A couple spelling mistakes on chart_tests.md

GitHub got more fussy about markdown

Fix typo: Update using_helm.md

The function chartutil.processImportValues was merging values unnecessarily and incorrectly merging --set values.

Closes #2331

bump download links to 2.4.2

they are currently set to 2.4.1.

Missed these on my PR last night

fix(docs): Updated non-working example in 'Using Helm' documentation

fix(docs): Fixing mariadb spelling mistake

Closes #2527

fix(plugins): exists --> exist

fix(tiller): Adds missing import back

PR #2513 was behind master when merged. Other commits were
added that required the use of the log package. This re-adds
that package.