Merge pull request #46 from farmersdog/antonbeza/success-without-link…

…ed-story

Currently builds fail if no Shortcut story is referenced in the branch name or PR title. 

This PR makes it so the build still passes even if no Shortcut story ID is found in the branch name or PR title.

### Changes
* Makes it so the PR title stays as-is if no Shortcut stories are referenced and passes the build
* Added some JSDocs
* Removed `getShortcutStory` function since it wasn't adding anything useful over the raw Shortcut client call

### Testing
* Wrote a medium sized test to confirm the core behavior
* Mocked the Shortcut client
* Manually tested that fetching from Shortcut worked using the included `createTitle.js` script