Using methods from userMessageHelpers in SGCompetitveStoryController and tests

#### What's this PR do?
Replaces logic in SGCompetitiveStoryController with methods from userMessageHelpers.

#### Where should the reviewer start?
`getNormalizedPhone` and `isValidPhone` are methods that exist in userMessageHelpers. So those are just straight up replaced. In cases where I'm just looking for a "yes" response, you'll see...
```
messageHelper.isYesResponse(messageHelper.getFirstWord(<some string here>))
```
This gets the first word of a string and checks whether or not it should evaluate to a "yes".

#### How should this be manually tested?
Running `npm test` should be sufficient. Otherwise, I also manually and successfully stepped through an entire Bully Text game with 2 players.

#### Any background context you want to provide?
`userMessageHelpers` was originally created to be used by the SGCreateFromMobileController. Using it here frees us from having duplicate code in two different places.

#### What are the relevant tickets?
SMS-64