main.c v1.04 (change the arguments global)

Now need not pass the arguments in the function startsws().
net.h v1.05(add function clientwrite)

Add the function clientwrite() declaration.
Modify the declaration of startsws();
http.c v1.02 (fix some bugs)

We don't want the source contain \r and \n. So ignore them when compute
the length.
Now can tolerate blanks after the path (instead of throw a 400 error).
net.c v1.08 (GET request)

The server now can response the GET request.
Just show the file which the client wants.
Add simple 403 and 404 error response.
Merge pull request #23 from lzhang25/master

main.c v1.04, net.c v1.08, http.c v1.02, net.h v1.05 (deal with GET request)  (need to be tested and modified later)