Fix #27 JS implementation

src/class/RNFetchBlobReadStream.js

 
     // register for file stream event
     let subscription = emitter.addListener(`RNFetchBlobStream+${this.path}`, (e) => {
-    
+
       let {event, detail} = e
       if(this._onData && event === 'data')
         this._onData(detail)
   onData(fn) {
     if(this.encoding.toLowerCase() === 'ascii')
       this._onData = (data) => {
-        fn(JSON.parse(data))
+        fn(data)
       }
     else
       this._onData = fn

src/fs.js

  * @return {Promise<Array<number> | string>}
  */
 function readFile(path:string, encoding:string, bufferSize:number):Promise<any> {
+  if(typeof path !== 'string')
+    return Promise.reject('Invalid argument "path" ')
   return RNFetchBlob.readFile(path, encoding)
 }
 
 function writeFile(path:string, encoding:string, data:string | Array<number>):Promise {
+  if(typeof path !== 'string')
+    return Promise.reject('Invalid argument "path" ')
   if(encoding.toLocaleLowerCase() === 'ascii') {
     if(!Array.isArray(data))
       Promise.reject(`Expected "data" is an Array when encoding is "ascii", however got ${typeof data}`)
   mv,
   cp,
   writeStream,
+  writeFile,
+  readFile,
   exists,
   createFile,
   isDir,