Fix some of the warnings reported by compilation with Scala 2.13.x

There are two remaining kinds of warnings, which cannot be fixed simply:

1.
[warn] .../scalac-scoverage-plugin/src/main/scala/scoverage/coverage.scala:39:80: object DeprecatedDoubleOrdering in object Ordering is deprecated (since 2.13.0): There are multiple ways to order Doubles (Ordering.Double.TotalOrdering, Ordering.Double.IeeeOrdering). Specify one by using a local import, assigning an implicit val, or passing it explicitly. See the documentation for details.
[warn]   def risks(limit: Int) = classes.toSeq.sortBy(_.statementCount).reverse.sortBy(_.statementCoverage).take(limit)
[warn]                                                                                ^

There are no Ordering.Double.TotalOrdering and Ordering.Double.IeeeOrdering classes in previous Scala versions.

2.
[warn] .../scalac-scoverage-plugin/src/test/scala/scoverage/ScoverageCompiler.scala:71:97: class Reporter in package reporters is deprecated (since 2.13.0): Use reflect.internal.Reporter
[warn] class ScoverageCompiler(settings: scala.tools.nsc.Settings, reporter: scala.tools.nsc.reporters.Reporter)

'reflect.internal.Reporter' class cannot be used because 'scoverage.ScoverageCompiler' class extends 'scala.tools.nsc.Global' class, and it requires 'scala.tools.nsc.reporters.Reporter' as a constructor parameter.

Author: gslowikowski

scalac-scoverage-plugin/src/main/scala/scoverage/report/CoverageAggregator.scala

@@ -28,7 +28,7 @@ object CoverageAggregator {
       if (coverageFile.exists) {
         val subcoverage: Coverage = Serializer.deserialize(coverageFile)
         val measurementFiles: Array[File] = IOUtils.findMeasurementFiles(dataDir)
-        val measurements = IOUtils.invoked(measurementFiles)
+        val measurements = IOUtils.invoked(measurementFiles.toIndexedSeq)
         subcoverage.apply(measurements)
         subcoverage.statements foreach { stmt =>
           // need to ensure all the ids are unique otherwise the coverage object will have stmt collisions

scalac-scoverage-plugin/src/test/scala/scoverage/CoverageMetricsTest.scala

@@ -21,7 +21,7 @@ class CoverageMetricsTest extends FreeSpec with Matchers {
       override def ignoredStatements: Iterable[Statement] = Seq()
     }
     metrics.branchCount shouldBe 0
-    metrics.branchCoverage - 1 shouldBe < (0.0001)
+    metrics.branchCoverage shouldBe 1.0 +- 0.0001
   }
 
   "no branches with no invoked statements should have 0% branch coverage" in {