Roll back Ivy to 2.3.0 for 0.13.5 for #1356

This is a fix for #1356.

Due to test failures at the last minute
- https://travis-ci.org/sbt/ivy/builds/25567318
- https://travis-ci.org/sbt/sbt/jobs/25567288

we might need to roll back Ivy back to 2.3.0 final. 
The reported version of sbt that worked was 0.13.2-M3, which uses Ivy 2.3.0.