Add general tips for setting up init.d scripts

[jesperronn]

Following up on #73 and #43, but in a general matter. This project could really benefit from a few working examples or a debugging example script for init.d processes.

I imaginge a script could be a boiled down version of a unicorn startup script. However, without the unicorn server. An example script could serve the purpose to verify that rvm-auto script actually works. That the correct user and the correct path is set up.

This would also make it easier to solve problems like the rvm error

Warning: PATH set to RVM ruby but GEM_HOME and/or GEM_PATH not set, see:
    https://github.com/wayneeseguin/rvm/issues/3212

(because rvm/rvm#3212 is not really relevant to init.d problems but discussing zsh integration).

I imagine the script could answer the following

• current user (running the script), to verify 'deployer' user
• rvm-auto path loading correctly
• ruby version being picked up correctly
• ruby gemset being picked up correctly
• perhaps the ability to call a gem in your deployed folder (unicorn --version, rails --version or similar)

I dont know about you, but I, at least, would greatly benefit from this. I would love to help, but as you can see from #73, I am not able for now to write a script that could answer the above.

However, if you could please share any snippets, examples, ideas, anything here. Then I will pick it up and make an attempt to extract it.

Thanks for your help!