Adding server mode

moto/s3/urls.py

@@ -1,9 +1,10 @@
-from .responses import all_buckets, bucket_response, key_response
+from .responses import bucket_response, key_response
 
-base_url = "https?://(.*).s3.amazonaws.com"
+url_bases = [
+    "https?://(?P<bucket_name>\w*)\.?s3.amazonaws.com"
+]
 
-urls = {
-    'https?://s3.amazonaws.com/$': all_buckets,
-    '{0}/$'.format(base_url): bucket_response,
-    '{}/(.+)'.format(base_url): key_response,
+url_paths = {
+    '{0}/$': bucket_response,
+    '{0}/(?P<key_name>\w+)': key_response,
 }