Stop stripping periods from multi-sentence titles

If a topic title has multiple sentences in it, it looks strange to strip
the trailing period off it, so we only want to do that automatically
when it's a single sentence.

tildes/tests/test_title.py

@@ -46,12 +46,19 @@ def test_whitespace_trimmed(title_schema):
 
 
 def test_trailing_periods_trimmed(title_schema):
-    """Ensure trailing periods on a title are removed."""
+    """Ensure trailing periods on a single-sentence title are removed."""
     title = "This is an interesting story."
     result = title_schema.load({"title": title})
     assert not result["title"].endswith(".")
 
 
+def test_multisentence_trailing_period_kept(title_schema):
+    """Ensure a trailing period is kept if the title has multiple sentences."""
+    title = "I came. I saw. I conquered."
+    result = title_schema.load({"title": title})
+    assert result["title"].endswith(".")
+
+
 def test_consecutive_whitespace_removed(title_schema):
     """Ensure consecutive whitespace in a title is compressed."""
     title = "sure   are  \n  a  lot    of     spaces"

tildes/tildes/schemas/topic.py

@@ -45,8 +45,14 @@ class TopicSchema(Schema):
 
         new_data = data.copy()
 
-        # strip any trailing periods
-        new_data["title"] = new_data["title"].rstrip(".")
+        split_title = re.split("[.?!]+", new_data["title"])
+
+        # the last string in the list will be empty if it ended with punctuation
+        num_sentences = len([piece for piece in split_title if piece])
+
+        # strip trailing periods off single-sentence titles
+        if num_sentences == 1:
+            new_data["title"] = new_data["title"].rstrip(".")
 
         return new_data