As I commented you need to use a StringIO  object and decode i.e c=pd.read_csv(io.StringIO(s.decode("utf-8"))) if using requests, you need to decode as .content returns bytes if you used .text you would just need to pass s as is s = requests.get(url).text c = pd.read_csv(StringIO(s)). 
A simpler approach is to pass the correct url of the raw data directly to read_csv, you don't have to pass a file like object, you can pass a url so you don't need requests at all:
c = pd.read_csv("https://raw.githubusercontent.com/cs109/2014_data/master/countries.csv")
print(c)
Output:
                              Country         Region
0                             Algeria         AFRICA
1                              Angola         AFRICA
2                               Benin         AFRICA
3                            Botswana         AFRICA
4                             Burkina         AFRICA
5                             Burundi         AFRICA
6                            Cameroon         AFRICA
..................................
From the  docs:
filepath_or_buffer :
string or file handle / StringIO
  The string could be a URL. Valid URL schemes include http, ftp, s3, and file. For file URLs, a host is expected. For instance, a local file could be file ://localhost/path/to/table.csv