bumped up version in README

Author: anthony-cros

README.md

@@ -34,7 +34,7 @@ The library is available for both Scala 2.12 and 2.13
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 It requires the following in your `build.sbt` file:
 ```
-libraryDependencies += "io.github.galliaproject" %% "gallia-core" % "0.2.0"
+libraryDependencies += "io.github.galliaproject" %% "gallia-core" % "0.3.1"
 ```
 
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