add function getKey

[oldfeel]

upload: function(file) {
    if (!file || file.size === 0) 
        return null;
    var key = file.preview.split('/').pop() + '.' + file.name.split('.').pop();
    if (this.props.prefix) {
        key = this.props.prefix + key;
    }

    if (this.props.uploadKey) {
        key = this.props.uploadKey;
    }
    this.setState({key: key})

    var r = request.post(this.props.uploadUrl).field('key', key).field('token', this.props.token).field('x:filename', file.name).field('x:size', file.size).attach('file', file, file.name).set('Accept', 'application/json');
    if (isFunction(file.onprogress)) {
        r.on('progress', file.onprogress);
    }
    return r;
},

getKey: function() {
    return this.state.key
},

[lenage]

@oldfeel whitespace 清一下吧