Added header to CHANGELOG.md

Former-commit-id: bb5b146b

CHANGELOG.md

-0.1
----
+# Changelog of GeDACCMU
+This file describes the improvements of each subsequent versions. Each version name is a git tag that can be checked out.
+
+v0.1
+----
 
 Important milestones comprise:
 - Par_forecast returns scientifically correct results.
@@ -12,8 +15,8 @@ In addition:
 - Generated doc using Sphinx
 
 
-0.2
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+v0.2
+----
 Numerous improvements aiming to optimise the code, the most important being:
 * The possibility to run forecasts in parallel using `mpi4py`
 * The possibility to save results during computation in `hdf5` or `ASCII` format.