small whitespace fixes

gallery_dl/extractor/danbooru.py

@@ -24,4 +24,4 @@ class DanbooruExtractor(JSONBooruExtractor):
 
     def __init__(self, match, config):
         JSONBooruExtractor.__init__(self, match, config, info)
-        self.api_url  = "https://danbooru.donmai.us/posts.json"
+        self.api_url = "https://danbooru.donmai.us/posts.json"

gallery_dl/extractor/e621.py

@@ -25,4 +25,4 @@ class E621Extractor(JSONBooruExtractor):
 
     def __init__(self, match, config):
         JSONBooruExtractor.__init__(self, match, config, info)
-        self.api_url  = "https://e621.net/post/index.json"
+        self.api_url = "https://e621.net/post/index.json"

gallery_dl/extractor/gelbooru.py

@@ -24,11 +24,11 @@ class GelbooruExtractor(XMLBooruExtractor):
 
     def __init__(self, match, config):
         XMLBooruExtractor.__init__(self, match, config, info)
-        self.api_url  = "http://gelbooru.com/"
-        self.params   = {"page":"dapi", "s":"post", "q":"index", "tags":self.tags}
+        self.api_url = "http://gelbooru.com/"
+        self.params = {"page":"dapi", "s":"post", "q":"index", "tags":self.tags}
 
     def update_page(self, reset=False):
         if reset is False:
             self.params["pid"] += 1
         else:
-            self.params["pid"]  = 0
+            self.params["pid"] = 0