Scalding 0.17.1 with 2.11 and 2.12 support

Changes of this release:

• Request for Scalding release 0.17.0 (#1641) … b1bf1be
• make ordered serialization stable across compilations (#1664) … 0f95484
• Remove unnecessary semicolon (#1668) 14d3f76
• Add tailrec annotation (#1671) 693e6b7
• Be more paranoid about Kryo registration order (#1673) 0b291f2
• Update sbt version to 0.13.15 (#1677) bf0e724
• Register all Boxed classes in Kryo (#1678) … c930bcd
• Fix serialization of KryoHadoop (#1685) … a72fd72
• Merge pull request #1686 from ttim/cherry_pick_0.17.x_changes … 9da38a1
• Fix stack overflow in typedPipeMonoid.zero (#1688) … 6bcb169
• A couple of fixes into the 0.17.x branch (#1695) … a6d3775
• Memory estimator changes to 0.17.x branch (#1700) … 9b8ea00