Update WebServer.h

Hi again. Here is a summary of the changes
- The recent patches did not compile. On Arduino 1.0.5 MAX_SOCK_NUM was missing so I included ethernet.h
- I added back write(const uint8_t *buffer, size_t size) which was removed with the addition of buffering
- I added printf for convenience
- I made reset & flushBuf public. 
I'll continue to use the current version and report any bugs. I think that it may be a good time to up the version number

Thanks