Bump mini_racer from 0.2.4 to 0.2.6
Bump mini_racer from 0.2.4 to 0.2.6

Bumps [mini_racer](https://github.com/discourse/mini_racer) from 0.2.4 to 0.2.6.
- [Release notes](https://github.com/discourse/mini_racer/releases)
- [Changelog](https://github.com/discourse/mini_racer/blob/master/CHANGELOG)
- [Commits](https://github.com/discourse/mini_racer/commits)
indentlabs/notebook,indentlabs/notebook,indentlabs/notebook