Speed improvements

Changes:
- Rewrite Box.
  - Process files during loading file list.
  - Delay file hash check. Use File.changed() to check if file changed.
  - Remove watch delay.
  - Parallel processing.
- Save rendered content in warehouse. It really saves a lot of time.
- Rewrite generate console.
  - Cache rendered content so we don't have to render it again.
  - Load file list from cache. Don't delete other files in public folder. Resolve #1310
  - Remove file stat check.
  - Parallel generating.
- Resolve race conditions.

Known issues:
- Parallel processing and parallel generating may cause race conditions. We have to solve this in warehouse.
- Tests are not updated yet.

lib/box/file.js

@@ -1,76 +1,20 @@
 'use strict';
 
 var fs = require('hexo-fs');
-var Promise = require('bluebird');
-
-var escapeBOM = fs.escapeBOM;
-var escapeEOL = fs.escapeEOL;
 
 function File(data) {
   this.source = data.source;
   this.path = data.path;
-  this.type = data.type;
   this.params = data.params;
-  this.content = data.content;
-  this.stats = data.stats;
-}
-
-function wrapReadOptions(options) {
-  options = options || {};
-  if (typeof options === 'string') options = {encoding: options};
-  if (!options.hasOwnProperty('encoding')) options.encoding = 'utf8';
-  if (!options.hasOwnProperty('cache')) options.cache = true;
-  if (!options.hasOwnProperty('escape')) options.escape = true;
-
-  return options;
-}
-
-function escapeContent(str) {
-  return escapeBOM(escapeEOL(str));
+  this.type = data.type;
 }
 
 File.prototype.read = function(options, callback) {
-  if (!callback && typeof options === 'function') {
-    callback = options;
-    options = {};
-  }
-
-  var self = this;
-  var content = this.content;
-
-  options = wrapReadOptions(options);
-
-  return new Promise(function(resolve, reject) {
-    if (!options.cache || !content) {
-      return fs.readFile(self.source, options).then(resolve, reject);
-    }
-
-    var encoding = options.encoding;
-    if (!encoding) return resolve(content);
-
-    var result = content.toString(encoding);
-    if (options.escape) return resolve(escapeContent(result));
-
-    resolve(result);
-  }).asCallback(callback);
+  return fs.readFile(this.source, options).asCallback(callback);
 };
 
 File.prototype.readSync = function(options) {
-  var content = this.content;
-
-  options = wrapReadOptions(options);
-
-  if (!options.cache || !content) {
-    return fs.readFileSync(this.source, options);
-  }
-
-  var encoding = options.encoding;
-  if (!encoding) return content;
-
-  var result = content.toString(encoding);
-  if (options.escape) return escapeContent(result);
-
-  return result;
+  return fs.readFileSync(this.source, options);
 };
 
 File.prototype.stat = function(options, callback) {
@@ -79,27 +23,10 @@ File.prototype.stat = function(options, callback) {
     options = {};
   }
 
-  options = options || {};
-
-  var stats = this.stats;
-  var cache = options.hasOwnProperty('cache') ? options.cache : true;
-  var self = this;
-
-  return new Promise(function(resolve, reject) {
-    if (stats && cache) return resolve(stats);
-
-    fs.stat(self.source).then(resolve, reject);
-  }).asCallback(callback);
+  return fs.stat(this.source).asCallback(callback);
 };
 
 File.prototype.statSync = function(options) {
-  options = options || {};
-
-  var cache = options.hasOwnProperty('cache') ? options.cache : true;
-  var stats = this.stats;
-
-  if (stats && cache) return stats;
-
   return fs.statSync(this.source);
 };