allow setting of keepalive handler

adds the keepalive keyword to the client LWRP so you can set a client
specific handler for keepalive events
[validate] validate sensu client and check names
Merge pull request #228 from portertech/validate

Validate Aensu client and check names          - Fixes issues/201
Merge pull request #184 from coffeepac/master

allow setting of keepalive handler