v0.5.7

• Fix: Ignore excessive whitespace in chunk header for Transfer-Encoding: chunked
  (#123 by @DangerLifter and @clue)

• Fix: Ignore invalid incoming Transfer-Encoding response header
  (#122 by @clue)

• Improve documentation for Client (and advanced Connector)
  (#111 by @jsor and #121 by @clue)

• Improve test suite by adding support for PHPUnit 6
  (#112 by @carusogabriel)