Make it clear that the version is now 0.6.0-dev

Author: utensil

galgebra/_version.py

@@ -5,4 +5,4 @@
 # 1) we don't load dependencies by storing it in __init__.py
 # 2) we can import it in setup.py for the same reason
 # 3) we can import it into your module
-__version__ = '0.5.2'
+__version__ = '0.6.0-dev'