Should be context in stead of this

Got errors when using `parseDom` with newer version of cheerio in certain cases
```
TypeError: Cannot read property 'textFormat' of undefined
    at Object.<anonymous> (/Users/janpotoms/Woorank/code/piccolo/node_modules/microformat-node/lib/parser.js:666:41)
```
fix another context/this issue
Update package.json
Merge pull request #11 from Woorank/fix-context

Should be context in stead of this