Sqids (pronounced "squids") is a small library that lets one generate
YouTube-like unique IDs from numbers.  It is good for link shortening,
fast and URL-safe ID generation, and decoding back into numbers for
quicker database lookups.

Good for:

  - Generating IDs for public URLs (e.g. link shortening)
  - Generating IDs for internal systems (e.g. event tracking)
  - Decoding for quicker database lookups (e.g. by primary keys)

Not good for:

  - Sensitive data (this is not an encryption library)
  - User IDs (can be decoded revealing user count)