Updated documentation

README.md

@@ -8,5 +8,31 @@ _rOCCI framework now consists of the following separately maintained parts:_
 
 _You can still install it by running:_
 ~~~
+gem install rake
 gem install occi
 ~~~
+
+Requirements
+------------
+
+### Ruby
+* at least version 1.8.7 is required
+* Ruby 1.9.3+ is recommended
+* RubyGems installed
+* rake installed (e.g., `gem install rake`)
+
+### Libraries/packages
+* libxslt1-dev/libxslt-devel
+* libxml2-dev/libxml2-devel
+* **only if using Ruby 1.8.7:** libonig-dev/oniguruma-devel (Linux) or oniguruma (Mac)
+
+### Examples
+For distros based on Debian:
+~~~
+apt-get install ruby rubygems ruby-dev libxslt1-dev libxml2-dev libonig-dev
+~~~
+
+For distros based on RHEL:
+~~~
+yum install libxml2-devel libxslt-devel ruby-devel openssl-devel gcc gcc-c++ ruby rubygems oniguruma-devel
+~~~