Add documentation to Unhasher impl for Fingerprint.
Add documentation to Unhasher impl for Fingerprint.

aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust