Clarify that pysolr is pip-installable

Author: alexwlchan

README.rst

@@ -36,9 +36,14 @@ Requirements
 Installation
 ============
 
-``sudo python setup.py install`` or drop the ``pysolr.py`` file anywhere on your
-PYTHONPATH.
+pysolr is on PyPI:
+
+.. code-block:: console
 
+   $ pip install pysolr
+
+Or if you want to install directly from the repository: ``sudo python setup.py install``, or drop the ``pysolr.py`` file anywhere on your
+PYTHONPATH.
 
 Usage
 =====