yet another URL library for Python

 URL is constructed from `str`:
 .
  >>> from yarl import URL
  >>> url = URL('https://www.python.org/~guido?arg=1#frag')
  >>> url
  URL('https://www.python.org/~guido?arg=1#frag')
 .
 All URL parts: scheme, user, passsword, host, port, path, query and fragment
 are accessible by properties:
 .
  >>> url.scheme
  'https'
  >>> url.host
  'www.python.org'
  >>> url.path
  '/~guido'
  >>> url.query_string
  'arg=1'
  >>> url.query
  <MultiDictProxy('arg': '1')>
  >>> url.fragment
  'frag'
 .
 All URL manipulations produces a new URL object:
 .
  >>> url.parent / 'downloads/source'
  URL('https://www.python.org/downloads/source')
 .
 Strings passed to constructor and modification methods are automatically
 encoded giving canonical representation as result::
 .
  >>> url = URL('https://www.python.org/путь')
  >>> url
  URL('https://www.python.org/%D0%BF%D1%83%D1%82%D1%8C')
 .
 Regular properties are percent-decoded, use `raw_` versions for getting
 encoded strings:
 .
  >>> url.path
  '/путь'
 .
  >>> url.raw_path
  '/%D0%BF%D1%83%D1%82%D1%8C'
 .
 Human readable representation of URL is available as `.human_repr()`:
 .
  >>> url.human_repr()
  'https://www.python.org/путь'