Added load module options: theme_watch, source_watch
Added `content` and `replace` to Create API
- content: replace property in yam
- replace: replace the file if exists
Added `getFilename` method to Create API
Added yfm.parse & yfm.stringify
Added `original_content` property to Post, Page schema
Disable login in debug mode
Expose `process` in hexo namespace
Added `getScaffold` method to Create API