Major C code rewrite to generate better documentation
Remove (VALUE) loop reference from rbuv_handle_t, use the path uv_handle->loop->data
Add documentation for module Rbuv
Rename Rbuv::Loop#uv_active_handles to Rbuv::Loop#ref_count
Don't run blocks passed to Rbuv::Loop#run (and friends) ON the first loop iteration but BEFORE

libuv does not need or take any advantage of running its public functions on, before or after a loop iteration.
Add rake task for generating documentation