Signed-off-by: Adam Reese <adam@reese.io>

Signed-off-by: Adam Reese <adam@reese.io>

ref(chartutil): move chart loading out of chartutil into new package
    add chart loader interface to allow lazy loading
feat(chart): create chart accessors
ref(*): cleanup requirements
ref(tiller): remove optional template engines
ref(tiller): simplify sorting releases and hooks
ref(*): code simplification
ref(hapi): move chart package out of hapi
ref(chart): add requirements and lock to Chart struct

Modified existing unit test to verify the changed behavior.
Removed debug print.

docs(helm): Added documentation about tpl function

This sorts templates by depth before sending them to the template
parser. Deepest templates are parsed first, with umbrella templates
parsed last. Since template definition names are LIFO, that means that
the highest level templates will claim the namespace.

Or, to put it simply, you can predictably override a child's defined
template by re-defining it in a parent chart.

Closes #2452

- Added tests for using a function inside a template that is evaluated using the "tpl" function

Implementation for #1978

The output of a rendered partial is not used and rendering it might fail if it expects different values

Adds the `required` function in enginge.go to support required
properties in values.yml. When a chart developer wishes to specify
intent in requiring a value, they can use this function to declare
an error message that gets returned when chart rendering fails
when a required value is not present in values.yml.

Closes #1580

This adds the {{.Capabilities}} object to the template variables so that
chart authors can write charts that are aware of teh Kubernetes
capabilities of the current cluster.

Closes #1608

This adds a fromYaml template function.

Closes #1604

This adds a function engine.FuncMap that returns a function mapping that
better represents the functions passed to a template. The linting logic
is reconfigured to use this function instead of the sprig.FuncMap
function.

Closes #1366

This adds the function toYaml to the Engine template functions.

Closes #1225

Closes #1076

This changes "pkg/chartutil".Files.Get to return a string, removes
"pkg/chartutil".Files.GetString, and adds
"pkg/chartutil".Files.GetBytes.

Closes #1020

This adds a context-aware template function called 'partial' that will
allow rendering other templates in a chart into a string value, which
can then be piped to other functions. Usage is something like
'{{partial 'path/to/template.yaml' | indent 2}}'

This might be a bad idea.

Closes #1005

Templates can now access the non-template files in a chart by using
the '{{.Files}}' map inside of a template.

Relates to #950

This fixes a bug in which passed-in values files were not correctly
merged into the chart's default values YAML data. I believe it also
fixes some other prioritization bugs in values merging.

The existing unit test was wrong (see TestCoalesceValues). It is
fixed now. Also added more tests to simulate issue #971.

In the course of writing this, I removed some vestigial code as
mentioned in #920.

Closes #971
Closes #920