Unit tests for Reddit memes

[Jaace]

Description

Added AVA support and Sinon (though unused in this current version). Fixed an issue where the URLs were 403ing because & was coming back from the Reddit API in the URL. Used text replace as encoding or sanitizing was not working.

Reference: #50

Steps to Test

1. node reddit.js should now work again.
2. npm test should show 3 passing tests.

Checklist

• I have tested these code changes and included the relevant urls and screenshots.
• I have updated our build tasks accordingly (if applicable).
• I have updated our documentation accordingly (if applicable).
• I have linted the code that I've included in this PR (if applicable).
• My code follows the code style of this project.
• My code is ready for review.

[cjwilburn]

LGTM! Thanks!