Pipenv: Pipfile parsing not fully TOML compliant

This exact concern appears to have been raised and dismissed in issue #613. At some point pipenv dropped proper support for quoted keys. If this is not the case then I'm hopeful I can be pointed to the specification used in order to better construct my Pipfiles.

The paragraphs pertaining to quoted and dotted keys in the Keys section of this README are relevant to this issue: https://github.com/toml-lang/toml#keys

Describe your environment

1. Debian 10
2. Python version: 3.6.4
3. Pipenv version: 10.1.2

Expected result

This Pipfile...

[[source]]
url = "https://pypi.python.org/simple"
verify_ssl = true
name = "pypi"

["requires"]
python_version = "3.6"

[packages]
motor = "*"

    [packages."discord.py"]
    git = "https://github.com/Rapptz/discord.py.git"
    ref = "rewrite"
    editable = true
    extras = ["voice"]

Should render the following dictionary... (parsed by toml and prettyprinted)

{'packages': {'discord.py': {'editable': True,
                             'extras': ['voice'],
                             'git': 'https://github.com/Rapptz/discord.py.git',
                             'ref': 'rewrite'},
              'motor': '*'},
 'requires': {'python_version': '3.6'},
 'source': [{'name': 'pypi',
             'url': 'https://pypi.python.org/simple',
             'verify_ssl': True}]}

Actual result

Traceback (most recent call last):
  File "/home/akirasama/.local/bin/pipenv", line 11, in <module>
    sys.exit(cli())
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/vendor/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/vendor/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/vendor/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/vendor/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/vendor/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/vendor/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/cli.py", line 433, in sync
    clear=clear, unused=unused, sequential=sequential
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/core.py", line 2389, in do_sync
    ensure_project(three=three, python=python, validate=False)
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/core.py", line 603, in ensure_project
    ensure_virtualenv(three=three, python=python, site_packages=site_packages)
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/core.py", line 548, in ensure_virtualenv
    python = ensure_python(three=three, python=python)
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/core.py", line 424, in ensure_python
    python = project.required_python_version
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/project.py", line 110, in required_python_version
    required = self.parsed_pipfile.get('requires', {}).get('python_full_version')
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/project.py", line 271, in parsed_pipfile
    return contoml.loads(toml.dumps(data, preserve=True))
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/patched/contoml/__init__.py", line 15, in loads
    elements = parse_tokens(tokens)
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/patched/prettytoml/parser/__init__.py", line 17, in parse_tokens
    return _parse_token_stream(TokenStream(tokens))
  File "/home/akirasama/.local/venvs/pipenv/lib/python3.6/site-packages/pipenv/patched/prettytoml/parser/__init__.py", line 32, in _parse_token_stream
    raise ParsingError('Failed to parse line {}'.format(pending.head.row))
prettytoml.parser.errors.ParsingError: Failed to parse line 11

Steps to replicate

$ pipenv lock