Add CHANGELOG

CHANGELOG.rst

+1.0.dev2
+========
+
+- Switch to Jinja templating
+
+1.0.dev1
+========
+
+Re-write of the metamodule generation:
+- Toolchain metamodules are deprecated and will only be generated for the existing toolchains
+- The octopus-dependencies module does now come in two variants min and full
+
+
+1.0.dev0
+========
+
+- Re-write of the old ``spack_setup.sh`` and ``software-manager``.