Adopt best practices with distributing portfiles

Reorganised packaging and added some notes for less experienced users
on how to get the development version of ansible installed using macports.

packaging/macports/.gitignore

@@ -0,0 +1,2 @@
+PortIndex
+PortIndex.quick

packaging/macports/README.md

@@ -2,6 +2,8 @@ This portfile installs ansible from the git repository, it will install the
 latest and greatest version of ansible. This portfile does not install the
 required dependancies to run in fireball mode.
 
+## Installing the stable version of ansible via macports
+
 If you wish to run a stable version of ansible please do the following
 
 First update your macports repo to the latest versions
@@ -11,3 +13,27 @@ First update your macports repo to the latest versions
 Then install ansible
 
   $ sudo port install ansible
+
+## Installing the devel version of ansible via macports
+
+To use this Portfile to install the development version of ansible one should
+follow the instructions at
+<http://guide.macports.org/#development.local-repositories>
+
+The basic idea is to add the _ansible/packaging/macports_ directory to your
+_/opt/local/etc/macports/sources.conf_ file. You should have something similar
+to this at the end of the file
+
+  file:///Users/jtang/develop/ansible/packaging/macports
+  rsync://rsync.macports.org/release/tarballs/ports.tar [default]
+
+In the _ansible/packaging/macports_ directory, do this
+
+  $ portindex
+
+Once the index is created the _Portfile_ will override the one in the upstream
+macports repository.
+
+Installing newer development versions should involve an uninstall, clean,
+install process or else the Portfile will need its version number/epoch
+bumped.