Issue#355 根据活动地址显示百度地图

在config/settings.yml中增加一个新的配置项
````yml
  # Used to generate event location map automaticlly with Baidu Map API.
  # You can request your access key from http://lbsyun.baidu.com/apiconsole/key
  # By default, with an empty string, this feature will be disabled.
  baidumap_ak: ''
````
默认baidumap_ak为nil则不启用百度地图。页面显示与以前一样。当将baidumap_ak设置为从百度申请的access key时，自动启用百度地图显示。效果如下：

活动编辑页面
![snip20130524_2](https://f.cloud.github.com/assets/1198651/559589/b0319802-c453-11e2-96ce-fa2c20db0df9.png)

活动展示页面边栏
![snip20130524_3](https://f.cloud.github.com/assets/1198651/559591/b6f26144-c453-11e2-874e-9db3b7f30811.png)

同时对keyup event 做了 debounce 处理