Simplifying standalone mm2-connect config

One of the nice things about kafka is setting up in the local environment is really simple. I was giving a try to the latest feature ie MM2 and found it took me some time to get a minimal setup running.
Default config provided assumes that there will already be 3 brokers running due to the default replication factor of the admin topics the mm2 connector creates.

This got me thinking that most of the people would follow the same approach I followed.
1. Start a single broker cluster on 9092
2. Start another single cluster broker on, let's say, 10002
3. Start mm2 by"./bin/connect-mirror-maker.sh ./config/connect-mirror-maker.properties"

What happened was I had to supply a lot more configs

This jira is created post discussion on the mailing list:
https://lists.apache.org/thread.html/%3CCAJXUdH13Kw3nAm3hO69WROzSyoVwUE1nXf9hKcbawC9R-3dnhA@mail.gmail.com%3E

cc ryannedolan