Wrong indentation of case do clause with pipeline

Hi everyone,

This issue happens with the `case do`. Elixir indentation should be this one:
```
variable
|> case do
nil ->
:noop
_ ->
:ok
end
```

But the elixir-mode does this, it places four spaces:
```
variable
|> case do
nil ->
:noop
_ ->
:ok
end
```