message: minor doc fix: controller.webexbot spelling
diff: @@ -93,7 +93,7 @@ controller.on('direct_message', function(bot, message) {
  When creating the Botkit controller, there are several platform-specific options available.
  -### Botkit.webex
  +### Botkit.webexbot
  | Argument | Description
  |--- |---
  | public_address | _required_ the root url of your application (https://mybot.com)
  @@ -104,7 +104,7 @@ When creating the Botkit controller, there are several platform-specific options
  | `limit_to_domain` | _optional_ email domain (@howdy.ai) or array of domains [@howdy.ai, @botkit.ai] from which messages can be received
  ~~~ javascript
  -var controller = Botkit.webex({
  +var controller = Botkit.webexbot({
  debug: true,
  log: true,
  public_address: 'https://mybot.ngrok.io',
  @@ -118,7 +118,7 @@ var controller = Botkit.webex({
  ### Webex rebrand
  -Back in April 2018, Cisco announced a [rebrand from Cisco Spark to Webex]().
  +Back in April 2018, Cisco announced a [rebrand from Cisco Spark to Webex](https://developer.webex.com/blog/blog-details-9738.html).
  In May 2018, starting with version **TODO**, Botkit reflected this rebrand by updated 'Spark' mentions from the framework API.
  **For backward compatibility purposes**, several references are now marked as deprecated, but still supported (except for Typescript code). Please migrate your code if your find references to:
  