Bump Gaia version to 0.3.1-beta (#1016)

Author: simone-gaia

README.md

@@ -205,7 +205,7 @@ When we are ready to release a new version of Gaia this is the process to follow
    ```shell
    git add -u
    git commit -m "Bump Gaia version to 0.3.0-beta"
-   git branch --set-upstream-to origin/gaia-release-0.3.0-beta
+   git branch --set-upstream-to origin gaia-release-0.3.0-beta
    # Create a PR to push the change into master.
    ```
 6. Create a tag reflecting the new version:

production/CMakeLists.txt

@@ -10,7 +10,7 @@ include(UseJava)
 enable_testing()
 
 # Set the project name.
-project(production VERSION 0.3.0)
+project(production VERSION 0.3.1)
 
 # Sets the pre-release version which will be appended to the
 # product version: 0.1.0-alpha.