Support DDG style bangs with bang at the end (#503)

DDG style bang searches can now have the bang (!) at the end of
the search (i.e. "bologna w!" will now redirect to wikipedia just like
"bologna !w" would)

app/utils/bangs.py

@@ -55,9 +55,10 @@ def resolve_bang(query: str, bangs_dict: dict) -> str:
     query = query.lower()
     split_query = query.split(' ')
     for operator in bangs_dict.keys():
-        if operator not in split_query:
+        if operator not in split_query \
+                and operator[1:] + operator[0] not in split_query:
             continue
-
         return bangs_dict[operator]['url'].format(
-            query.replace(operator, '').strip())
+            query.replace(operator if operator in split_query
+                          else operator[1:] + operator[0], '').strip())
     return ''

test/test_routes.py

@@ -36,6 +36,11 @@ def test_ddg_bang(client):
     assert rv._status_code == 302
     assert rv.headers.get('Location').startswith('https://www.reddit.com')
 
+    # Move '!' to end of the bang
+    rv = client.get('/search?q=gitlab%20w!')
+    assert rv._status_code == 302
+    assert rv.headers.get('Location').startswith('https://en.wikipedia.org')
+
     # Ensure bang is case insensitive
     rv = client.get('/search?q=!GH%20whoogle')
     assert rv._status_code == 302