flesh out install a little

docs/installing.rst

@@ -4,6 +4,19 @@ Installation
 Python & OS Support
 -------------------
 
-fastkml works with CPython version 2.6, 2.7, 3.2, 3.3, 3.4
+fastkml works with CPython version 2.6, 2.7, 3.2, 3.3, 3.4 and is
+continually tested with TravisCI for these version. The tests break
+intermittently for pypy and pypy3 so they are not tested but should work,
+Jython and IronPython are not tested but *should* work.
 
-fastkml works on Unix/Linux, OS X, and Windows
+.. image:: https://api.travis-ci.org/cleder/fastkml.png
+    :target: https://travis-ci.org/cleder/fastkml
+
+fastkml works on Unix/Linux, OS X, and Windows.
+
+Install it with `pip install fastkml` or `easy_install fastkml`.
+
+If you use it extensively or need to process big kml files consider
+installing lxml_ as it speeds up processing.
+
+.. _lxml: https://pypi.python.org/pypi/lxml