Performance Optimizing:

1, write_watch start when need to write and stoped when nothing in
queue.
bug fix:

1, SetNonBlock returns bool-type, but handle as int32_t. which will make
a busy-waiting.
bug fix:

1, add int32_t result in new connection
update:

1, divide Closure in two pieces. one for GC, one for work
update:

1, change get_controller()/get_channel() to controller()/channel().
bug fix:

1, change SerializerToFileDescriptor to SerializerToString. because data
lose while write.
bug fix:

1, not all data read from buffer.
2, add example net-db .
bug fix:

1, ControllerMeta.failed not initialized. which made a mistake when write.
bug fix:

1, connection close while buffer too long.
2, example update.
update:

1, delete unused code.
2, add submodules libev and leveldb(used in example)
add needed static file.
replace SetNonBlock with socket(,,SOCK_NONBLOCK),
        accept4(,,SOCK_NONBLOCK)
bug fix
add setup.py
link close
add default sock
move dep into deps directory
add more field in controllermeta
change libtool to cmake
unneeded file