Update default.rb

Added port config.
Update default.rb
Update nginx_ice_site.erb

Updated so that port can be specified for nginx server.
Update README.md

Added new config in readme.
Upgrading the artifact cookbook version to avoid issues reported
by users using librarian.
Merge pull request #12 from akshah123/nginx_port

Allow Nginx port configuration
Merge pull request #13 from mdsol/feature/upgrade-artifact-cookbook-version

Upgrading the artifact cookbook version to avoid issues reported
Updating changelog
Merge branch 'release/0.2.11' into develop
Fixed bug where if the public_hostname is not provided and niginx_port is other than 80, the generated hostname in nginx configuration is incorrect as it doesn't include custom port.