Auto-sanitize user URL input

[lorennorman]

"What's your Twitter username?"

Goals:

• Developer Usability:
  • easy to create URL forms
  • easy to use later as text or links or whatever
• End-User Usability:
  • good labels and placeholders
  • permissiveness: accept and normalize lots of potential inputs
  • good error detection and error messages when permissiveness fails

Permissiveness examples:

• lorennorman
• twitter.com/lorennorman
• http://twitter.com/lorennorman

...should all resolve to:

https://twitter.com/lorennorman

Existing gems? Roll our own?