ENH: Add helper to fetch images from URLs

Author: effigies

nibabel/filebasedimages.py

@@ -574,3 +574,13 @@ def to_bytes(self, **kwargs):
         file_map = self.make_file_map({'image': bio, 'header': bio})
         self.to_file_map(file_map, **kwargs)
         return bio.getvalue()
+
+    @classmethod
+    def from_url(klass, url):
+        """ Fetch image from remote location and construct an image
+
+        Requires the ``requests`` library to be installed.
+        """
+        import requests
+        res = requests.get(url)
+        return klass.from_bytes(res.content)