Add note about installing on Ruby 1.8.7 [ci skip]

README.md

@@ -15,7 +15,7 @@ fog is the Ruby cloud services library, top to bottom:
 
     sudo gem install fog
 
-Now type `fog` to try stuff, confident that fog will let you know what to do. 
+Now type `fog` to try stuff, confident that fog will let you know what to do.
 Here is an example of wading through server creation for Amazon Elastic Compute Cloud:
 
     >> server = Compute[:aws].servers.create
@@ -27,10 +27,31 @@ Here is an example of wading through server creation for Amazon Elastic Compute
     >> server.destroy # cleanup after yourself or regret it, trust me
     true
 
+## Ruby 1.8.7
+
+The maintainers of this project, in concert with the maintainers of Ruby,
+**strongly** recommend using the latest patchlevel of Ruby 1.9.2 or later.
+[As of July 1, 2013, Ruby 1.8.7 is no longer officially maintained.][retired]
+This means fixes will no longer be provided, even for known security
+vulnerabilities.
+
+[retired]: http://www.ruby-lang.org/en/news/2013/06/30/we-retire-1-8-7/
+
+With this caveat, if you wish to bundle `fog` into your application on Ruby
+1.8.7, you must add the following line to your `Gemfile`.
+
+    gem 'nokogiri', '~>1.5.0'
+
+Also, ensure that you are using LibXML version 2.8.0, since there is an
+[issue with LibXML version 2.9.0][issue829] ([and 2.9.1][issue904]).
+
+[issue829]: https://github.com/sparklemotion/nokogiri/issues/829
+[issue904]: https://github.com/sparklemotion/nokogiri/issues/904
+
 ## Collections
 
 A high level interface to each cloud is provided through collections, such as `images` and `servers`.
-You can see a list of available collections by calling `collections` on the connection object. 
+You can see a list of available collections by calling `collections` on the connection object.
 You can try it out using the `fog` command:
 
     >> Compute[:aws].collections