Don't parse root/property class names with consecutive dashes

[gRegorLove]

<div class="h-entry h-----">
<p> <a href="http://example.com/post" class="u-in-reply--to">http://example.com/post posted:</a> </p>
<span class="p-name">Too many dashes</span>
<span class="p--acme-leading">leading dash</span>
<span class="p-acme--middle">middle dash</span>
<span class="p-acme-trailing-">trailing dash</span>
</div>

Currently parses:

{
    "items": [
        {
            "type": [
                "h-----",
                "h-entry"
            ],
            "properties": {
                "name": [
                    "Too many dashes"
                ],
                "-acme-leading": [
                    "leading dash"
                ],
                "acme--middle": [
                    "middle dash"
                ],
                "acme-trailing-": [
                    "trailing dash"
                ],
                "in-reply--to": [
                    "http://example.com/post"
                ]
            }
        }
    ],
    "rels": {},
    "rel-urls": {},
    "debug": {
        "package": "https://packagist.org/packages/mf2/mf2",
        "version": "v0.4.1",
        "note": [
            "This output was generated from the php-mf2 library available at https://github.com/indieweb/php-mf2",
            "Please file any issues with the parser at https://github.com/indieweb/php-mf2/issues"
        ]
    }
}

Expected output via mf2py dev

{
    "rels": {}, 
    "items": [
        {
            "type": [
                "h-entry"
            ], 
            "properties": {
                "name": [
                    "Too many dashes"
                ]
            }
        }
    ], 
    "rel-urls": {}, 
    "debug": {
        "source": "https://github.com/microformats/mf2py", 
        "version": "1.1.0", 
        "markup parser": "html5lib", 
        "description": "mf2py - microformats2 parser for python"
    }
}

Per spec update: microformats/microformats2-parsing#31