Fix(challenges): Change challenge toasts copy

common/app/routes/challenges/redux/completion-saga.js

@@ -42,7 +42,7 @@ function submitModern(type, state) {
     if (type === types.checkChallenge) {
       return Observable.of(
         makeToast({
-          message: `${randomCompliment()} Go to next challenge.`,
+          message: `${randomCompliment()} Go to your next challenge.`,
           action: 'Submit',
           actionCreator: 'submitChallenge',
           timeout: 10000

common/app/routes/challenges/redux/next-challenge-saga.js

@@ -64,7 +64,7 @@ export default function nextChallengeSaga(actions$, getState) {
         return Observable.of(
           updateCurrentChallenge(nextChallenge),
           resetUi(),
-          makeToast({ message: 'Your next challenge arrived.' }),
+          makeToast({ message: 'Your next challenge has arrived.' }),
           push(`/challenges/${nextChallenge.block}/${nextChallenge.dashedName}`)
         );
       } catch (err) {