2.4.0 stopped installing development versions by default. This allows
the user to re-enable that support by setting --devel.

Closes #2407

This reverts commit 4222d6de.

Closes #2311

- [ ] Added tests for --repo flag on `helm fetch` command
- [ ] Also added tests for (pkg/repo).FindChartInRepoURL

Closes #2393

* resolves #2089

Fixes issues/2398 - helm plugin remove does not works as expected

- [ ] plugin remove option is coded to remove multiple plugins, but instead returns error when more than one plugin is requested to be removed.
- [ ] plugin remove does not show any error/message for non-existent plugin.

Partially fixes issues/2385 - helm install silently updates the plugin, if it pre-existed

Fixes issues/2384 - helm plugin install installs a default version in case requested version is not available

The current methodology generated its own RS slice instead of using
a helper method that uses a `clientset`. This caused some issues where
`FindNewReplicaSet` always returned `nil`. This switches the method and
removes some unneeded API calls and code.

Closes #2426

    Reverted the version of mergo to a version that was known to work
    with both kubernetes and sprig.

    Closes #2376

chore(tiller): bump Sprig to 2.11.0

This adds the `merge` function, among other things.

fix(releaseutil): remove newline on SplitManifests

fixes #2158

fix(create): incorrect URL in default NOTES.txt

Return as not ready if it new RS is nil

fix(*): handle unreleased versioning

Releases are locked to avoid parallel changes

fix(tiller): fix TOML panic

ref(getter): flatten the getter package tree

feat(helm): add service account flag to helm init

Add support for zsh to helm completion

This flattens the getter package tree, adds tests, and changes a little
bit of the terminology to follow Go idioms. This also makes much of the
getter API private to begin with. This will give us more flexibility in
the future.

Adds an `unreleased` flag to the version if not building from HEAD of a
tag. The compatibility check is bypassed if the client or server are
unreleased.

fixes #2110

helps with half of #2224

chore(ci): bump go 1.8.1

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

Fail template execution if included template fails