commonmark 0.17.1

• Reorganized block parsing in a more modular way. There is now a blocks property of the parser that contains information about each type of block, which is used in parsing. Ultimately this will make it easier to extend the library, but the project is still only partially completed.
• Code cleanup and simplification, with some performance optimizations.
• Removed version from bower.json. Bower takes version from tags.
• Initialize some properties at beginning of 'parse'. This fixes some mistakes in source position when the same Parser object was used to parse multiple times (#3).
• Made parsing of backslash escapes a bit more efficient.
• Removed refmap parameter of InlineParser.parse(). Instead, set the refmap property before running the parser.
• Set _string_content to null after using, allowing it to be GCd.
• Removed _strings; just append to _string_content. This gives better performance with v8.
• Format benchmarks so that samples are linked.
• Added in-browser benchmark.
• Added API documentation to README.
• xml renderer: use sourcepos attribute, not data-sourcepos.
• Changed license to 2-clause BSD. Added clause for spec.