Beautify CHANGELOG

Add some headings to the version numbers in the CHANGELOG to make it
more readable.

Change-Id: I86f2784b7ff3e386c2466fe8c3aa3aae78a8d036
Reviewed-on: https://gerrit.causes.com/30171
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>