Update JLD2 requirement to 0.6.3 in /test (#115)

Updates the requirements on [JLD2](https://github.com/JuliaIO/JLD2.jl) to permit the latest version.
- [Release notes](https://github.com/JuliaIO/JLD2.jl/releases)
- [Changelog](https://github.com/JuliaIO/JLD2.jl/blob/master/CHANGELOG.md)
- [Commits](JuliaIO/JLD2.jl@v0.0.1...v0.6.3)

---
updated-dependencies:
- dependency-name: JLD2
  dependency-version: 0.6.3
  dependency-type: direct:production
...

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test/Project.toml

@@ -15,6 +15,7 @@ BenchmarkTools = "1"
 Documenter = "1"
 Graphs = "1.4.1"
 InteractiveUtils = "1"
+JLD2 = "0.6.3"
 MetaGraphs = "0.7, 0.8"
 SimpleTraits = "0.9"
 Test = "1"