 
       config :ex_twilio, api_version: "2015-05-06"
   """
-  def api_version, do: @api_version
+  def api_version, do: Application.get_env(:ex_twilio, :api_version) || "2010-04-01"
 
   @doc """
   Return the combined base URL of the Twilio API, using the configuration 

  
      config :ex_twilio, account_sid: "YOUR_ACCOUNT_SID"
  """
  def account_sid, do: @account_sid

  @doc """
  Returns the Twilio Auth Token for your account. Set it in `mix.exs`:

      config :ex_twilio, auth_token: "YOUR_AUTH_TOKEN"
  """
  def auth_token,  do: @auth_token

  @doc """
  Returns the domain of the Twilio API. This will default to "api.twilio.com",


      config :ex_twilio, api_domain: "other.twilio.com"
  """
  def api_domain,  do: Application.get_env(:ex_twilio, :api_domain) || "api.twilio.com"

  @doc """
  Returns the version of the API that ExTwilio is going to talk to. Set it in
