A bucket name in the path can be migrated to a custom k8s domain
name. This is in preperation for that.

This pass through fixed formatting, examples, and technical information
to reflect the current state of Helm. Also added some pointers for
using a regular webserver.

The previous index.yaml example was missing a few fields, notably the
'created' timestamp.

Closes #1348

This adds the `--url` flag to examples.

Closes #1343

This implements a new index file format for repository indices. It also
implements a new format for requirements.yaml.

Breaking change: This will break all previous versions of Helm, and will
impact helm search, repo, serve, and fetch functions.

Closes #1197

The old form is marked deprecated.

Relates to #1196

Use the same format as the Open Container Initiative for a digest
string. https://github.com/opencontainers/image-spec/blob/master/descriptor.md#digests-and-verification

Fixes #1166

Signed-off-by: Jess Frazelle <me@jessfraz.com>

Closes #809