Add some optimization codes.

Convert indentation to Spaces.
[nginx] Rename nginx original configuration filename (nginx.conf.bak -> nginx.conf.orig).
[nginx] Add gzip target mimetype.
[nginx] Add worker_rlimit_nofile option.
[nginx] Add timeout options.
[nginx] Add default charset.
[nginx] 
[nginx] Change default mimetype to text/html.
[nginx] Change worker connections to 2048.
[nginx] Change worker processes to auto.