Test that the coalesced key is properly removed for all YAML null syntax options, but not for empty string

- Note that this covers all YAML null syntax options:
  ref: http://yaml.org/type/null.html
- Note that we do a nil comparison because the encoding/yaml package parses
  YAML properly and any variation of null, Null, NULL, or ~ is converted to nil
  by the time we get here.

feat(*): use kubernetes 1.7

Adds charts in "charts\" directory to dependencies

Remove mention of the Service type from the ingress documentation

Capitalize 'helm' text in init.go.

[scripts/get] makes sudo an optional dependency

feat(helm): Correct capitalization and punctuation for all user facing text

ref(helm): consolidate vars() function

$EUID is readonly, so it should be save to test against it.

Thanks for the tip @thomastaylor312 !

Reduce indent in code block

Remove confusing 'if' from install.md

charts.md updates

The "if" might confuse reader

Avoid using $* multiple times

If the execution user is already the root user, this avoids requireing
sudo to be installed within the environment. Which might helo in CI
environments.

Updating docs to prioritize `requirements.yaml` over `charts/` directory.

As `requirements.yaml` is the recommended strategy, let's document that first to make sure no one jumps the gun and goes ahead to implement manual deps via `charts/` just because they didn't read the whole section.

Fixed helm test sample.

The current sample doesn't work as documented.

New sample based on https://github.com/kubernetes/charts/pull/1156.

ref(helm): make FakeReleaseClient public

Update standard label docs

Added more tests to test following comibnations of subcharts and requirements.yaml
- [ ] subcharts not specified in requirements.yaml
- [ ] some subcharts specified in requirements.yaml while others should be picked directly from "charts\"
- [ ] all subcharts specified in requirements.yaml without alias
- [ ] subcharts specified in requirements.yaml with alias is already tested

Update plugins.md

* give an uniform check for release process

* fixed as the review of adamreese: update the err message when releasename is empty and update the test units.

* fixed as the review of bacongobbler: add more detail information to return message. the regex rule is added to the return message.

Align docs to what we currently recommend as best practices.

Fix markdown syntax in doc

Added omitempty to Requirements struct

Update README with links to docs.helm.sh

Improve chart examples