Upload helper v0.1

It is a plugin for resize,convert and compress the picture
so that it can be used as an avator

##API

uploadHelper(event,imgSize,returnType,callback)

###this is the function for resizing and compressing the picture ###param: ####event: the event of the filechange ####imgSize: [Object] the size of output picture,the obj has two key(width&height px), as it use canvas to draw a picture,more pixels means more storage peace. ####returnType['Blob' or 'DataUri'] choose the type of output file.DataUri can be a value of img.src and Blob can be appended into formdata and post it.

callback(file)

 when the work is done,uploadHelper will run the callback with the result image file as arguments[0]

```javascript fileToDataUrl(file[blob],callback) ``` ###this is the function for converting blob to dataURI

##note:the demo will help you to know how to use it.