XD-2377-2 Add `$scope.$apply` to `about` controller
XD-2331: Single node recovery on disconnect

When a single node server disconnects and reconnects to ZK
(for instance when running on a laptop that goes to sleep)
the leader election routine was failing an assert because
the CuratorFramework was not in STARTED state. This was
happening because the container listener forces a client
shutdown and reconnect to guarantee that all its ephemeral
nodes are cleaned up. This connection is the same one
being passed to the leader election routine.

The fix is to only force the container to recreate the
CuratorFramework if it is not in the STARTED state.
The state transition of SUSPENDED -> LOST -> RECONNECTED
where the framework has restarted seems to happen
consistently when the machine running the process
goes to sleep and wakes up.

XD-2373: Distributed test should verify container shutdown

After each test, block execution until admin indicates that
all containers have been unregistered from ZK.

Destroy streams before container shutdown

Increased state transition timeout

Some tests require deployment to a container after it joins
the cluster. Since there is a mandatory waiting period before
new containers are assigned deployments (15 seconds by default)
the wait period for the verify stream/job state methods has been
increased.
XD-2409 Changing correlation-strategy-expression

- this will avoid some issues ecountered with SpEL (SPR-12502)

- using "payload.class.name" seems to work in all cases
XD-2387 Kafka AcceptanceTests
XD-2333 Add Kafka integration test

- Add kafka test support class that checks for kafka server availablity
  on localhost
- This uses zk server available on default connect string `localhost:2181`
- Add test for verifying kafka source and sink having both the source/sink
  on the same test case will make sure the topic that gets the data by
  kafka sink is actually read by kafka source
- Handle Zk connect exceptions
- Fix create/delete topic in Before/After
- Remove explicit sleep by setting kafka source consumer
  timeout to -1 (blocking)
- Fix import statements
XD-2426: Use new Travis CI build env, add caching

- test cache behavior
- Add debug
- use -PwikiBranch=origin/master
XD-2386 Acceptance tests for tcp-client source

connect to a nc (netcat) server that returns the following value UOHSO638abna9beqw12.
The netcat can be run using the following:
(Mac)
while true; do nc -l -c  8782 < index.html; done
(*nix)
while true; do nc -l -C  8782 < index.html; done

where index contains UOHSO638abna9beqw12

See spring-xd-integration-test/src/scripts for scripts that
launch the nc process as described above.