Ignore not readable file and others 

做了一些修改，上传文件夹的时候，不可读的文件提示并跳过，而不是直接崩掉。文件名里有\的跳过，算好了校验码但是上传的时候发现文件没了的跳过。这样可以建立一个backup账户定期备份上传，敏感文件设为不可读即可，同步home的时候遇到了一些问题，所以有了后面两个修改。希望能有所帮助。

In this version, when encountering a file that is not readable when uploading a folder, it will skip the file and prompt out some message in verbose mode. On Linux, file name containing '\\' is allowed, also when uploading my home directory that contains cache file for Firefox and at the same time I use the browser, cache may got removed which makes bypy stop immediately. I just want to offer some improvement, maybe it is not what you want. Anyway, decisions are yours.