Added Mac OS X specific installation instructions

- created new doc folder
- removed doc folder from .gitignore
- included and updated instructions as mentioned in issue #59
- updated the README with a hint on the Mac OS X specific instructions

.gitignore

@@ -11,5 +11,4 @@ tmp
 log
 coverage
 vendor
-doc
 collection

README.md

@@ -23,6 +23,10 @@ To use rOCCI with Java, you need JRE 6 or 7. To build rOCCI for Java, you need J
 
 Installation
 ------------
+
+**[Mac OS X has some special requirements for the installation. Detailed information can be found in
+doc/macosx.md.](doc/macosx.md)**
+
 To install the most recent stable version
 
     gem install occi

doc/macosx.md

@@ -0,0 +1,27 @@
+# rOCCI on Mac OS X
+
+## Installation
+
+To use a recent version of Ruby on Mac OS X, a few preparations are needed. Unfortunately, Apple did complicate the
+process in the past, thus a detailed step by step is provided here:
+
+1. Install the latest version of Xcode either
+[from the Mac OS X App Store](itms://itunes.apple.com/de/app/xcode/id497799835?mt=12#) or by downloading it from
+[[http://developer.apple.com]] and then installing the package.
+2. Open Xcode, then download and install the Xcode command line tools (Menu->Xcode->Preferences->Downloads)
+3. In the Terminal, install RVM with `curl -L https://get.rvm.io | bash -s stable`
+4. Read the plattform requirements for your specific setup by running `rvm requirements` in the Terminal. Execute any
+tasks mentioned there for installing Ruby 1.9.3 (you can ignore hints for Ruby 1.8.7). If you need to install additional
+packages it is recommended to use Homebew for it (unless you already use MacPorts). To install Homebrew paste the
+following in your Terminal `ruby -e "$(curl -fsSL https://raw.github.com/mxcl/homebrew/go)"`
+5. Install Ruby 1.9.3 with `rvm install ruby-1.9.3`
+
+Now that you have Ruby 1.9.3 installed, you can intall rOCCI.
+
+To install the most recent stable version
+
+    gem install occi
+
+To install the most recent beta version
+
+    gem install occi --pre