Add '--end' option to 'start' command

So far we have implement the client code. Now we have to wait for
hamsterlib to implement the backend functionality.

Closes #145

hamster_cli/hamster_cli.py

@@ -287,22 +287,32 @@ def _start(controler, raw_fact, start, end):
 
 
 @run.command(help=help_strings.STOP_HELP)
+@click.option('--end', nargs=1, default=None, help=_(
+    "Specify an end date other than *now* ('%Y-%m-%d')"))
 @pass_controler
-def stop(controler):
+def stop(controler, end):
     """Stop tracking current fact. Saving the result."""
-    _stop(controler)
+    _stop(controler, end)
 
 
-def _stop(controler):
+def _stop(controler, end=None):
     """
     Stop cucrrent 'ongoing fact' and save it to the backend.
 
+    Args:
+        end (str, optional): Adjusted end time of the fact. Defaults to ``now``.
+
     Returns:
         None: If successful.
 
     Raises:
         ValueError: If no *ongoing fact* can be found.
+        ValueError: If ``--end`` was passed but can not be recognized.
     """
+    if end:
+        end_time = datetime.datetime.strptime(end, '%Y-%m-%d').time
+        end = datetime.datetime.combine(datetime.date.today(), end_time)
+
     try:
         fact = controler.facts.stop_tmp_fact()
     except ValueError: