Make game_handler support starting a game with a range of playeres.

Allow a game to start even if `max_players` is not reached.
Adding a new command `play game` to start a game if the
number of players is between max and min no. of players.
Make tests pass with the new change.

zulip_bots/zulip_bots/bots/connect_four/test_connect_four.py

@@ -53,6 +53,8 @@ class TestConnectFourBot(BotTestCase):
 `start game`
 * To start a game against another player, type
 `start game with @<player-name>`
+* To play game with the current number of players, type
+`play game`
 * To quit a game at any time, type
 `quit`
 * To end a game with a draw, type

zulip_bots/zulip_bots/bots/game_handler_bot/test_game_handler_bot.py

@@ -111,6 +111,8 @@ class TestGameHandlerBot(BotTestCase):
 `start game with @<player-name>`
 * To start a game with the computer, type
 `start game with` @**test-bot**
+* To play game with the current number of players, type
+`play game`
 * To quit a game at any time, type
 `quit`
 * To end a game with a draw, type

zulip_bots/zulip_bots/game_handler.py

@@ -72,6 +72,8 @@ class GameAdapter(object):
 `start game`
 * To start a game against another player, type
 `start game with @<player-name>`{}
+* To play game with the current number of players, type
+`play game`
 * To quit a game at any time, type
 `quit`
 * To end a game with a draw, type
@@ -167,6 +169,9 @@ class GameAdapter(object):
             elif content.lower().startswith('start game'):
                 self.command_start_game(message, sender, content)
 
+            elif content.lower().startswith('play game'):
+                self.command_play(message, sender, content)
+
             elif content.lower() == 'accept':
                 self.command_accept(message, sender, content)
 
@@ -323,6 +328,21 @@ class GameAdapter(object):
             return
         self.join_game(game_id, sender, message)
 
+    def command_play(self, message: Dict[str, Any], sender: str, content: str) -> None:
+        game_id = self.get_invite_in_subject(
+            message['subject'], message['display_recipient'])
+        if game_id is '':
+            self.send_reply(
+                message, 'There is not a game in this subject. Type `help` for all commands.')
+            return
+        num_players = len(self.get_players(game_id))
+        if num_players >= self.min_players and num_players <= self.max_players:
+            self.start_game(game_id)
+        else:
+            self.send_reply(
+                message, 'Join {} more players to start the game'.format(self.max_players-num_players)
+            )
+
     def command_leaderboard(self, message: Dict[str, Any], sender: str, content: str) -> None:
         stats = self.get_sorted_player_statistics()
         num = 5 if len(stats) > 5 else len(stats)