Problem: if cluster isn't ready, HAVE READER commands get lost

Solution: in test case, wait 250 msec before starting tests. In
reality, we may need some other synchronization mechanism, or a
retry to resend HAVE READER until command times out.

Also, set cluster interconnect to 250 msec.
Expanded src/zpipes_test_cluster

- invalid read/write action no longer closes pipe writer/reader
- basic clustering read/write now works (needs breaking)
- removed animation and debug tracing
Merge pull request #35 from hintjens/master

Finished up basic cluster test case