setup nginx for load balancing, setting HOME variable in unicorn_init, and fix for missing nginx log directory when web is a non-release role

- (temporary?) fix to problem in unicorn_init script whereby HOME variable is not set (possible alternative to https://github.com/bruno-/capistrano-unicorn-nginx/pull/11)
- create log directory for nginx if web is a non-release role
- connect over TCP/IP if there are multiple app roles and setup nginx for load balancing
I did test this. I get the same message as you do, but this is only an info message. It does not stop the capistrano script. I've tested this on Digital Ocean (Ubuntu 14.04), as well as a local VirtualBox VM (Ubuntu 12.04).

INFO[e1e9e4bb] Finished in 0.506 seconds with exit status 0 (successful).
DEBUG[476c9cb4]          System start/stop links for /etc/init.d/unicorn_vjw_edg_mx already exist.

I'm happy to remove this from this pull request. I also like your suggestion for overwriting the config files every times the `setup` task is invoked. I added this functionality because it I thought it was there for a reason.