Move old source code to ``src_old``.

Prepare for new version.
Update ``gm2chrome`` to latest version.
Rewrite grunt file. (use coffee.)
Rewrite build process.

To generate the extension, you can run:

```
$ make
```
Ignore build directory.
Add coffee lint config.
Add develop task.
Port douban subject page.
Port reader recommend.
Remove outdated TODO.
Port subject search page.
Port doulist page.
Minor changes.
Update ``gm2chrome`` to fix random require scripts order.
Bump version, remove legacy version.

Porting finish! =D
Merge pull request #52 from bcho/wip/coffee

使用 coffeescript 重写了脚本, v0.5.0