keepAlive: initial import

https://github.com/gmetais/YellowLabTools/commit/41ddd4961f43bbd94445d1068f0678b077a357a3#diff-9e9a4c8ee146efdc4ae7c2272a2991ad
keepAlive: add logging
keepAlive: fix a typo
keepAlive: add test cases
keepAlive: update metadata and README
Merge pull request #433 from macbre/keep-alive

keep-alive related metric