XMLHttpRequest.setLog and Blob.setLog not working 

Should change these lines `number` to `level`

[/src/polyfill/Blob.js#L54](https://github.com/wkh237/react-native-fetch-blob/blob/master/src/polyfill/Blob.js#L54)
[/src/polyfill/XMLHttpRequest.js#L87](https://github.com/wkh237/react-native-fetch-blob/blob/master/src/polyfill/XMLHttpRequest.js#L87)
