Name and mention name should be set automatically

[jimmycuadra]

Name ("real name" in Slack) and mention name ("username" in Slack) should be automatically assigned with the values in the Slack integration config when the bot connects.

[dsmorse]

There is also a minor mistake in the README It says:

Note: When using lita-slack, the adapter will overwrite the bot's name and mention name with the values set on the server, so config.robot.name and config.robot.mention_name will have no effect.

While it's true that it won't control the bots name in slack. config.robot.name does still control the name shown in the help response.
Not sure if its better to fix the README or try to get the help response to use the slack bot's name