Bump html-proofer from 3.16.0 to 3.17.0

Bumps html-proofer from 3.16.0 to 3.17.0.

Commits

• 5badc4e 💎 bump to 3.17.0
• 5969f09 Merge pull request #592 from gjtorikian/rubocop
• 9052b65 minor fixes
• 0c20549 lint
• 67a29e8 Merge pull request #590 from gjtorikian/support-local-cache
• 14d3f06 Merge pull request #591 from gjtorikian/check-source
• 4cf141f test source tags
• 09b1899 stupid ordering stuff
• cbcd0aa Remove needless duplication
• ac382e7 fix tests
• Additional commits viewable in compare view