v4.5.0 — stream input in bounded memory

Added

• analyze_lines() and hash_lines() take lines one at a time — an open
  file, a pipe, a generator — so an embedder can analyse a log without
  reading it into a string (#38).

Changed

• petit streams its input in bounded memory (#38, replacing #5). It used to
  read the whole input into one string, build an entry for every line and
  keep every entry in its groups: 1.4 GB of memory for a 96 MB, 1M-line
  secure log. It now keeps each group's count and a few samples, and the
  same log takes 28 MB for --hash and every graph and 36 MB for
  --wordcount, and still 28 MB for a 384 MB, 4M-line log. Output is byte-identical
  for every mode and fixture.
• A file is read in passes: every framer surveys it line by line, the
  drivers vote on records sampled across the whole of it, then it is
  parsed. Framing and driver choice are exactly what they were.
• A pipe is read once. petit holds its first 4 MB (HEAD_CHARS, the same
  as the JSON framer's limit); a pipe that ends there is read exactly like
  a file. A longer one is framed and parsed by what its first 4 MB chose,
  and a later record the driver can't read falls back to RawEntry on its
  own rather than sending the whole input back to be re-read.
• --graph finds its range and counts in one pass, keeping counts per
  time bucket and merging buckets once they are too fine to be drawn.
• --hash is about 25% faster and --wordcount more than twice as fast:
  Filter.scrub() built a debug log message for every stopword on every
  key even when debug logging was off, and --wordcount scrubs each
  distinct word once.

Fixed

• The container image's version label said 3.1.1.