Add README.md (#82)

* Add README.me

Mainly to add notes about tinyxml2 versions, resolves #79.

* Add information about patched tinyxml2 version

README.md

@@ -0,0 +1,10 @@
+# rospack
+A command-line tool for retrieving information about ROS packages available on the filesystem.
+
+## Installation
+
+Install this with [catkin](http://wiki.ros.org/catkin).
+
+#### tinyxml2
+
+With tinyxml2 versions 4.0.0 and 4.0.1 XML parsing of ROS packages will fail for `<?xml-model ...` lines due to a bug (see [#77](https://github.com/ros/rospack/issues/77)). To fix this use versions 2.X, 3.X or >=5. Additionally the ROS apt repositories provide a patched version (4.0.1-2) which also works with rospack for all platform/architecture pairs targeted by ROS Lunar.