Update README.md (#55)

Change `target-name` to `subteam` in documentation to reflect changes

Author: rickycodes

README.md

@@ -87,5 +87,5 @@ You can read more about these option in the [API](#API) section below
 
 - **`icon-url`** _(optional)_. Url to the avatar used for the bot in Slack. If not set this defaults to the avatar in this repository.
 - **`username`** _(optional)_. The name of the bot as it appears on Slack. If not set this defaults to `MetaMask bot`.
-- **`target-name`** _(optional)_. Use this if you want to ping an individual or subset of individuals on Slack using `@`.
+- **`subteam`** _(optional)_. Use this if you want to ping a subteam of individuals on Slack using `@`.
 - **`channel`** _(optional)_. Use this if you want to post to a channel other than the default: `metamask-dev`.