Fixes the breakage that https://github.com/flutter/flutter/pull/4092 would cause.
* New Material Design calculator example. (Attempt 2 after git fetch upstream). * Responded to code review. * Second round of code review.
This moves all the bot-related files to `dev/bots`, hiding it from our home page in github. Also, simplifies the travis setup, though that doesn't do any difference to the performance sadly.