SEO: Generate human-readable url path slugs for homophone sets

Examples:
 - `www.homophone.com/h/vane-vein-vain`
 - `www.homophone.com/h/overbuild-overbilled`
 - `www.homophone.com/h/recepit-reseat`

Slugs would be generated automatically based on URL encoded versions of the words, but would need to be updatable and maintain a history of previous slugs to not break permalinks.

Use the slug as permalink.

*Note: this URL interestingly has an apostrophe in it `http://www.gingersoftware.com/english-online/spelling-book/confusing-words/its-it%27s`*