util|scrooge|finagle: Update to Scala 2.13.1

Problem/Solution

Update util, scrooge, and finagle to all cross build
with Scala 2.13.1. We need to also update the
`scoverage` plugin here to deal with an issue where
plugins need to be specified to be fully cross versioned
(that is published with their full scala version, e.g., `2.13.0`
instead of just `2.13`) because Scala is not binary compatible
between minor releases and something changed between
2.13.0 and 2.13.1. The `scoverage` plugin version `1.6.1`
appears to work properly.

Differential Revision: https://phabricator.twitter.biz/D444211

.travis.yml

@@ -91,6 +91,7 @@ before_cache:
 scala:
   - 2.11.12
   - 2.12.8
+  - 2.13.1
 
 jdk:
   - openjdk8

build.sbt

@@ -142,7 +142,7 @@ def jdk11GcJavaOptions: Seq[String] = {
 }
 
 val withTwoThirteen = Seq(
-  crossScalaVersions += "2.13.0",
+  crossScalaVersions += "2.13.1",
   libraryDependencies += scalaCollectionCompat
 )
 

project/plugins.sbt

@@ -7,5 +7,5 @@ addSbtPlugin("com.twitter" % "scrooge-sbt-plugin" % releaseVersion)
 
 addSbtPlugin("com.typesafe.sbt" % "sbt-site" % "1.3.0")
 addSbtPlugin("io.get-coursier" % "sbt-coursier" % "1.0.0-RC13")
-addSbtPlugin("org.scoverage" % "sbt-scoverage" % "1.5.1")
+addSbtPlugin("org.scoverage" % "sbt-scoverage" % "1.6.1")
 addSbtPlugin("pl.project13.scala" % "sbt-jmh" % "0.3.4")