Fixed process didn't exit in debug mode
Domain module fallback
Fixed error log
Print error message with process.stderr
Fixed load.js watch. Expose theme config in hexo namespace.

TODO:
- Fixed file2.watch next
Changed post render flow.
Now you can use `hexo-config()` in stylus to get global and theme config.

Example:

#foo
  background: hexo-config('foo-background-color')