* Remove Tiller reference from the docs

Signed-off-by: Martin Hickey <martin.hickey@ie.ibm.com>

* Update comments after review

- https://github.com/helm/helm/pull/4788#discussion_r226037034
- https://github.com/helm/helm/pull/4788#discussion_r226037064
- https://github.com/helm/helm/pull/4788#discussion_r226037806
- https://github.com/helm/helm/pull/4788#discussion_r226038492
- https://github.com/helm/helm/pull/4788#discussion_r226039202
- https://github.com/helm/helm/pull/4788#discussion_r226039894



Signed-off-by: Martin Hickey <martin.hickey@ie.ibm.com>

To match the convention of `helm install`, `helm uninstall` is the inverse.

Other tangential changes in this PR:

- StatusDeleting has been changed to StatusUninstalling
- StatusDeleted has been changed to StatusUninstalled
- `helm list --deleted` has been changed to `helm list --uninstalled`
- `helm list --deleting` has been changed to `helm list --uninstalling`
- `helm.DeleteOption` and all delete options have been renamed to `helm.UninstallOption`

I have not made any changes to the "helm.sh/hook-delete-policy", "pre-delete" and "post-delete" hook annotations because

1. it's a major breaking change to existing helm charts, which we've commited to NOT break in Helm 3
2. there is no "helm.sh/hook-install-policy" to pair with "helm.sh/hook-uninstall-policy", so delete still makes sense here

`helm delete` and `helm del` have been added as aliases to `helm uninstall`, so `helm delete` and `helm del` still works as is.

This raises the limit from 14 to 53 chars based on the Kubernetes 1.4
name limit.

Closes #1528

Consistently add spacing for '{{ $foo }}'

This adds a detailed document on writing templates in Helm. This is NOT
a best-practices guide, but a thorough introduction to templates in
Helm.