message: Add delete method to in-memory store
diff: @@ -979,6 +979,10 @@ function Botkit(configuration) {
  cb('No ID specified');
  }
  },
  + delete: function(team_id, cb) {
  + delete(botkit.memory_store.teams[team_id]);
  + cb();
  + },
  all: function(cb) {
  cb(null, botkit.memory_store.teams);
  }
  @@ -996,6 +1000,10 @@ function Botkit(configuration) {
  cb('No ID specified');
  }
  },
  + delete: function(user_id, cb) {
  + delete(botkit.memory_store.users[user_id]);
  + cb();
  + },
  all: function(cb) {
  cb(null, botkit.memory_store.users);
  }
  @@ -1013,6 +1021,10 @@ function Botkit(configuration) {
  cb('No ID specified');
  }
  },
  + delete: function(user_id, cb) {
  + delete(botkit.memory_store.channels[channel_id]);
  + cb();
  + },
  all: function(cb) {
  cb(null, botkit.memory_store.channels);
  }
  