Up to sbt 0.13.5; deprecation warnings in build files.
Build for 2.11.1 by default, 2.10.4 in cross; turn on more warnings.
Stricter numerics; workaround for SI-8649.
Remove Comonadic of Commit.  Works around SI-8649.
Mention when Comonadic Commit can return.
Scala 2.11, build cleanup.

* Remove some warning suppression.

* Main build for 2.11.1, secondary for 2.10.4.

* Up to sbt 0.13.5.

* Work around SI-8649.