• Fixed a regression introduced in 1.60. Older versions of this library would
  match dates pretty match anywhere in a string, so "%Y-%m-%d" would match a
  string like "abcd1234-12-30efgh". This is probably too permissive, but we
  definitely want to match on word boundaries so that we match
  "log.2016-03-31". Based on a PR from YASUTAKE Kiyoshi. GitHub #3.