Wildcard sub-domains not supported readme

[tzeejay]

Hey,

I found #26 Multiple Domains in which you explained that wildcards do not work with Let's Encrypt but I would like to see this stated in the readme.

I have not looked at the Let's Encrypt specification but it makes sense. Would be nice if you could add it. I would do it myself and create a pull request but I thought it might be better if you do it in your writing style.

Thanks for the work on the script. Works incredibly well. I used it on 64-bit Ubuntu and OSX 10.10

[diafygi]

Correct, wildcards will not be supported by this script since Let's Encrypt does not support issuing wildcard domains using the http-01 verification method.