Whitespace Updates and Bugfixes

Bugfixes:

• Ensure empty properties is an object {} rather than array [] (#171)
• Ensure the parser does not mutate the DOMDOcument passed in (#174)
• Fix for multiple class names in backcompat parsing (#156)

Microformats Parsing Updates:

• New algorithm for plaintext values (#168 and parsing issue #15)
• Always resolve URLs from u- properties even when not from a link element (Parsing issue #10)

Other Updates:

• Improved test coverage