minor bugfixes and improved last_action view

cool; happy to upgrade this.  Three comments:

1. it's been suggested that you shouldn't use the point release here unless you know it to be significant.  When I go to build and push the gem, I get warnings when we have it represented this way.  I think the core idea is to be as permissive as possible in terms of letting folks use their existing gems.

2.  I'd like to move airbrake out of the core at some point.