0.26.3

• Added a keep_headers argument to _recorder.record and
  Recorder.dump_to_file to preserve named headers (for example Date)
  that are otherwise stripped as verbose defaults, so a signed response can be
  recorded and later verified. Matching is case-insensitive. See #763
• Fixed the element type exposed by CallList so static type checkers infer
  Call values when iterating, indexing, or filtering recorded calls. See #722
• Fixed query_string_matcher (and the query matching auto-applied to a
  registered URL's own query string) discarding blank-valued query params
  (b=), which caused requests with an extra or missing blank param to
  match incorrectly. See #804
• Fixed fragment_identifier_matcher treating opaque fragments (those without
  =, e.g. /users/5) as always equal, so a required fragment matched a
  different one or none at all. See #806