Add stream loaders, revise JSON formats.

[jheer]

• Breaking: Drop sync fromCSV, etc. methods. Replace with async parseCSV, etc.
• Breaking: Drop custom Arquero JSON format with embedded schema. It provides little if any additional value (as the schema does not include type information), and I don't have any evidence that people use it.
• Add support to load data from input readable streams.
• Add full streaming readers for CSV, fixed width, and NDJSON formats.
• Add support for gzip and deflate decompression of input streams.
• Add parseArrow, parseCSV, parseFixed, and parseJSON methods for async parsing. These methods replace the prior fromCSV, etc. methods, and can take both input streams and pre-loaded data (text or binary, in the case of Arrow).
• Expand parseJSON and toJSON to support a JSON type property, for control over row-oriented, column-oriented, and newline-delimited (NDJSON) formats.
• Update build, including package.json use of the browser property, for more targeted node/web separation.
• Update test cases to reflect changes.