Change Jenkiexs.Builds.details/2 to be coherent with ! convention

[GPrimola]

I noticed something in Jenkiexs.Buids.details/2 but didn't want to change in the abovementioned PR because it's not its purpose.

Jenkiexs.Builds.details/2 uses Client.get!/3 as follows:

  def details(job_name, build_number) do
    case Client.get!("/job/#{job_name}/#{build_number}/api/json") do
      %{status_code: 200, body: body} ->
        build = new(job_name, body)
        {:ok, build}

      %{status_code: status, body: body} ->
        {:error, "Got status #{status} with body #{inspect(body)}."}
    end
  end

What do you think about changing that request to Client.get/3 and then creating a Jenkiexs.Builds.details!/2 just to keep the API consistent?

Originally posted by @dflima in #18 (comment)