jQuery File Upload, only single image and rename before uploading

I am using the JQuery File Upload plugin.

I want to limit upload to one image, and replace if another image is selected, and rename before uploading to the server.My html code

<span class="btn btn-success fileinput-button">
    <i class="glyphicon glyphicon-plus"></i>
    <span>Add files...</span>
    <input id="fileupload" type="file" name="files[]"> 
</span>

I tried to make few changes in file

jquery.fileupload.js

but no success.