Fix exporting cheerio module

cheerio is intended to be used as below:

```javascript
var cheerio = require('cheerio'),
    $ = cheerio.load('<h2 class="title">Hello world</h2>');
```

So we should use `import * as cheerio from "cheerio"` in TypeScript.
However, `cheerio` was defined with `export default` in cheerio.d.ts.

cheerio/cheerio-tests.ts

@@ -1,6 +1,6 @@
 /// <reference path="cheerio.d.ts" />
 
-import cheerio from 'cheerio';
+import * as cheerio from 'cheerio';
 
 /*
  * LOADING

cheerio/cheerio.d.ts

@@ -262,5 +262,5 @@ interface CheerioAPI extends CheerioSelector {
 declare var cheerio:CheerioAPI;
 
 declare module "cheerio" {
-    export default cheerio;
+    export = cheerio;
 }