correct indentation for multiclause anonymous functions

[tonini]

This fixes #184

Behavior before

defmodule X do
  def func do
    Enum.filter([1,2,3],
      fn(1) -> true
      (2) -> false
        (_) -> true
      (3) -> true
        (_) -> true
      end)
  end
end

Behavior after

defmodule X do
  def func do
    Enum.filter([1,2,3],
      fn(1) -> true
        (2) -> false
        (_) -> true
        (3) -> true
        (_) -> true
      end)
  end
end