Remove streaming interface from core

[wooorm]

Now:

var unified = require('unified');
var parse = require('rehype-parse');
var rehype2remark = require('rehype-remark');
var stringify = require('remark-stringify');

var processor = unified()
  .use(parse)
  .use(rehype2remark)
  .use(stringify);

process.stdin
  .pipe(processor)
  .pipe(process.stdout);

Future:

 var unified = require('unified');
+var stream = require('unified-stream');
 var parse = require('rehype-parse');
 var rehype2remark = require('rehype-remark');
 var stringify = require('remark-stringify');
 
 var processor = unified()
   .use(parse)
   .use(rehype2remark)
   .use(stringify);
 
 process.stdin
-  .pipe(processor)
+  .pipe(stream(processor))
   .pipe(process.stdout);