Fix bug in release script due to typo.

* Fix collection typo
* Create shared command to setup 2.11 builds
* Alter snapshot detection to allow more flexible milestone versioning.
* Remove cusotm isSnapshot key for new sbt 0.13.2 isSnapshot key.


Review by @eed3si9n cc> @paulp

Also, please WAIT for travis to report success/failure before merging.