Tag Spack version 0.9

- Tagging a version to include all that's happened since 0.8.17

- This is in anticipation of merging `features/cflags` and
  `features/newarch`, which will break the spec format.

- 1.0 will likely come after those.

lib/spack/spack/__init__.py

@@ -105,7 +105,7 @@
 
 # Version information
 from spack.version import Version
-spack_version = Version("0.8.15")
+spack_version = Version("0.9")
 
 #
 # Executables used by Spack