##网络请求的简单封装
###功能及用法 ####1.GET请求数据
+(void)getSessionRequestDataWithUrlString:(NSString *)urlStr andSuccess:(SuccessBlock)successBlock;
####2. POST请求数据
+(void)postSessionRequestDataWithUrlString:(NSString *)urlStr andBody:(NSData*)bodyData andSuccess:(SuccessBlock)successBlock;
####3.下载文件
+(void)downloadFileWithUrlString:(NSString *)urlStr andSuccess:(DownloadBlock)downBlock;
####4.带进度条的下载文件
+(void)downloadFileWithUrlString:(NSString *)urlStr andProgress:(ProgressBlock)pBlock andSuccess:(DownloadBlock)downBlock;
####5.断点续传
#####5.1 开始下载
+(SessionHttpRequest *)startDownloadFileWithUrlString:(NSString *)urlStr andProgress:(ProgressBlock)pBlock andSuccess:(DownloadBlock)downBlock;
#####5.2 暂停
-(void)cancleDownloadTask;
#####5.3 继续下载
-(void)continueDownloadTask;