Adding OSX macports installation instructions

* adjustments based  on Jacob's comments

doc/prepare.md

@@ -32,6 +32,8 @@ during installation.
 Please read [the prerequisites for all platforms](#prerequisites-for-all-platforms).
+#### Install OS X prerequisites using homebrew
+
 ```
 brew tap homebrew/dupes
 brew tap homebrew/versions
@@ -40,6 +42,18 @@ bundle config build.eventmachine --with-cppflags=-I/usr/local/opt/openssl/includ
 npm install phantomjs-prebuilt@2.1.12 -g
 ```
+#### Install OS X prerequisites using macports
+
+We are using PostgreSQL-9.5 in the following example. If you want to use another version, please adjust paths accordingly.
+
+```
+sudo port install git redis libiconv postgresql95-server icu pkgconfig cmake nodejs4 go openssl npm2
+bundle config build.eventmachine --with-cppflags=-I/opt/local/include/openssl
+sudo npm install phantomjs-prebuilt@2.1.12 -g
+echo 'export PATH=/opt/local/lib/postgresql95/bin/:$PATH' >> ~/.profile
+```
+
+
 ### Ubuntu
 Please read [the prerequisites for all platforms](#prerequisites-for-all-platforms).