- Simplify RStream/WStream API and make it more consistent with libuv.
- Move into the event loop layer(event subdirectory)
- Remove uv_helpers module.
- Simplify job/process internal modules/API.
- Unify RStream and WStream into a single structure. This is necessary because
libuv streams can be readable and writable at the same time(and because the
uv_helpers.c hack to associate multiple streams with libuv handle was removed)
- Make struct definition public, allowing more flexible/simple memory
management by users of the module.
- Adapt channel/job modules to cope with the changes.
