Change case on the "already invited" message

lib/slack-invite.js

@@ -30,7 +30,7 @@ export default function invite({ org, token, email, channel }, fn){
       if (providedError === 'missing_scope' && needed === 'admin') {
         fn(new Error(`Missing admin scope: The token you provided is for an account that is not an admin. You must provide a token from an admin account in order to invite users through the Slack API.`));
       } else if (providedError === 'already_invited') {
-        fn(new Error('You have already been invited to slack. Check for an email from [email protected].'));
+        fn(new Error('You have already been invited to Slack. Check for an email from [email protected].'));
       } else if (providedError === 'already_in_team') {
         fn(new Error(`Sending you to Slack...`));
       } else {