default CLI to json-compact server encoding

Avoid using BSER in the CLI because we have some issues with it for
persistent connections.

Addresses https://github.com/facebook/watchman/issues/11

Longer term, I'd like to default BSER on again, but I'll do that once
we're running with libphenom.

Note that 88c84d6597227d71bfca3136e4567fa08048af2c works around this by
documentation.  We'll keep those docs in place for a couple of releases
before taking them out to allow folks some time to upgrade to the newer
"fixed" version.