agent: Validate datacenter is valid. Fixes #169.
ui: show session name if there is one
agent: Adding new CheckUpdateInterval config
agent: Allow CheckUpdateInterval to be zero
agent: Defer sync based on CheckUpdateInterval
website: Document the check_update_interval config
agent: leave inSync until the defer runs
agent: Update config test to handle zero value CheckUpdateInterval
Merge pull request #204 from hashicorp/f-check-freq

Add deferred sync for check output
agent: Prevent anti-entropy from doing early sync of check output
consul: Provide output for serfHealth check. Fixes #176.
agent: Fixing merge of CheckUpdateInterval
agent: Cleanup handling of defer checks
ui: add some basic tests
ui: add nodeShow test