Spin off libraries kj-async and capnp-rpc, so that people who don't want them can avoid their large footprint.

Implement two-party network.  The first RPC call over a socket took place at 2013-11-08 14:46:43 -0800 and completed successfully.

Add tests for actually receiving multiple signals and multiple polls at once, not just listening for them.

fix typos in error message and comment

Add zero arg constructor and `getType` to DynamicValue::Pipeline

Make Schema default constructors produce consistent, non-crashy values.  This improves the dynamic interface's robustness, particularly when exceptions are disabled.