Bump nokogiri to 1.6.1
Adds legacy MD5 fingerprinting scheme

Older applications used this scheme for generating trace
signatures. This brings them back such that migrations from
older versions to new ones can occur.
Rename md5 to legacy fingerprint
Update docs with how to use fingerprint strategies
Merge pull request #680 from csaunders/md5_fingerprints

Adds legacy MD5 fingerprinting scheme
Some cleaning and standardising.
Added deploy notifications.