Change processor.parser, processor.compiler signatures

[wooorm]

parser(vfile, settings, processor) > parser(doc, vfile)
compiler(vfile, settings, processor) > compiler(tree, vfile)

That makes it more similar to transformers, and allows for settings to be removed (GH-23).

---

var parse = require('./parse')
var proc = unified().use(parse, {b: true}).data('settings', {a: true});

proces.parse('foo', console.log);

parse.js:

module.exports = parser;

Parser.prototype.parse = parse;
Parser.prototype.defaults = {c: true};

// Invoked when attaching.
function parser(options) {
  var proc = this;
  var LocalParser = proc.parser = unherit(Parser);
  LocalParser.prototype.defaults = xtend(LocalParser.prototype.defaults, options);
  LocalParser.prototype.processor = proc;
}

// Constructed just before parsing.
function Parser(contents, file) {
  // allow use without unified.
  var settings = this.processor ? this.processor.data('settings') : {};
  this.doc = contents;
  this.file = file;
  this.settings = xtend(this.defaults, settings);
}

// Constructed when parsing, with `this` as an instance of Parser.
function parse() {
  this.settings; //=> {a: true, b: true, c: true}
  return this.start(); // ...or something
}