Renames for better compatibility.

[mbostock]

In D3 3.x, the request-and-parse methods were renamed:

• d3.csv ↦ d3.requestCsv
• d3.html ↦ d3.requestHtml
• d3.json ↦ d3.requestJson
• d3.text ↦ d3.requestText
• d3.tsv ↦ d3.requestTsv
• d3.xml ↦ d3.requestXml

This was needed in part because this repo, d3-dsv, defines two objects:

• d3.csv
• d3.tsv

These objects then expose methods:

• d3.csv.parse
• d3.csv.parseRows
• d3.csv.format
• d3.csv.formatRows
• d3.tsv.parse
• d3.tsv.parseRows
• d3.tsv.format
• d3.tsv.formatRows

The downside of this renaming is that the commonly used methods were renamed (and longer), while the less commonly used methods stayed the same.

However, another option would be to retain the short names for requests:

• d3.csv
• d3.html
• d3.json
• d3.text
• d3.tsv
• d3.xml

And rather than exposing d3.csv and d3.tsv objects, expose the methods directly:

• d3.csvParse
• d3.csvParseRows
• d3.csvFormat
• d3.csvFormatRows
• d3.tsvParse
• d3.tsvParseRows
• d3.tsvFormat
• d3.tsvFormatRows