io_wrapper add read() error check, run_cgi.py modify testing case
select hang problem fixed, write command to socket use non-blocking ... etc.

1. select hang problem: after calling select(), fd_set changed,
   so you should reset fd_set before next calling select().

2. write command to socket use non-blocking, but this test bad. Maybe
   changed next commit.

3. connect_server: open server fd add NONBLOCKING flag.

4. dump file to socket use line reading(read once command at once), instead of binary reading.

5. cgi::http_get_parameters() add empty value checking.