Search form should have an aria-label

[joshsmith01]

How can this bug be reproduced?

1. Perform a Chrome Dev Tools Audit with at least Accessibility and SEO options selected
2. Accessibility audit result indicates that the Search form input could use a label

What did you expect to happen?
I expected the form input to have a label associated with it to pass Accessibility audits
What happened instead?
Accessibility audit of this particular item failed

Please List the Following:

• OS & version: Mac OS 10.13.6
• Node version (node -v) [Node v4+ is required] : v9.11.1
• FoundationPress version (see line 3 in package.json): 2.10.4
• Foundation version (found in node_modules/foundation-sites/package.json) : 6.4.3

Include Test Case (if applicable):
Screenshot of failing item:
https://cl.ly/38ec95594f6d