Remove Typescript default export Was causing an error since there's a duplicate default export. ``` > rollup -c rollup.config.js
Remove Typescript default export
Was causing an error since there's a duplicate default export.
```
> rollup -c rollup.config.js

🚨   Duplicate export 'default' (206:22) in /Users/mac/Github/slippy-grid/node_modules/@turf/
turf/index.js
undefined (206:22)

npm ERR! Darwin 16.4.0
npm ERR! argv "/usr/local/bin/node" "/usr/local/bin/npm" "run" "rollup"
npm ERR! node v6.9.5
npm ERR! npm  v3.10.10
npm ERR! code ELIFECYCLE
npm ERR! slippy-grid@1.2.2 rollup: `rollup -c rollup.config.js`
npm ERR! Exit status 1
```

stebogit/turf,stebogit/turf,tilemapjp/turf,dpmcmlxxvi/turf,Turfjs/turf,hooplert/jesper,Turfjs/turf,hooplert/jesper,Turfjs/turf,tilemapjp/turf,tilemapjp/turf,hooplert/jesper,dpmcmlxxvi/turf,dpmcmlxxvi/turf,stebogit/turf