Merge pull request #127 from alfredodeza/master

bump the version and changelog for a release
v1.3.1
update the changelog for 1.3.1

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
Fix variable name in unsupported-platform error case.
Merge pull request #128 from omcnet/fix-unsupported-platform-exception

Fix variable name in unsupported-platform error case.