Escape triple quotes in docstring

[uohzxela]

  embed_template :lib, """
  defmodule <%= @mod %> do
    @moduledoc \"""
    Documentation for <%= @mod %>.
    \"""

    @doc \"""
    Hello world.

    ## Examples

        iex> <%= @mod %>.hello
        :world

    \"""
    def hello do
      :world
    end
  end
  """