Reduce comment spacing to single tab.

Make comment for PathValue more explanatory.

Fix inverted equaility check and update error message.

Capitalize "yaml" in error message. Remove empty var from test error message.

'fmt.Errorf' is unnecessary when checking for 0 length path in Values.PathValue
due to the lack of formatting. Add test covering changes.

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.

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

Dependencies should be processed even if they are not added to requirements.yaml
Fixes https://github.com/kubernetes/helm/issues/2599

This was needed to get correct sha for requirements.yaml and requirements.lock
Fixes https://github.com/kubernetes/helm/issues/2598

```
- 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

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

Closes #2331

Fixes https://github.com/kubernetes/helm/issues/2383

Sample `requirements.yaml` I used for test purpose was for wordpress chart

```dependencies:
- name: mariadb
  version: 0.5.10
  repository: https://kubernetes-charts.storage.googleapis.com/
  alias:
  - db1
  - db2
  - db3
```

This fixes a TOML panic by replacing one parser library with another.
The older library did not gracefully handle reflection issues, and so
was prone to panic. The new one is not great, but it doesn't seem to
panic.

Closes #2271

Fixes issues/2276: helm dependency list hangs if run on large directory

This fixes a segfault that was the result of assigning to a property of
a nil pointer.

Closes #2244

Rebase on kubernetes v1.6

Fixes a bug where tags and conditions specified in values.yaml were not being respeceted, causing incorrect loading of subcharts.

Closes #2139

Fix codefences and nits in charts.md. Correct whitespace in charts. Add clarity to description of ImportValues requirements field.

Implements a mechanism in requirements.yaml to allow the import
and re-parenting of value table from child chart.

Closes #1995