Add info for Pycairo support and slightly reorder things

Author: mbonnefoy

README.md

@@ -31,22 +31,28 @@ Assuming that you built your own mapnik from source, and you have run `make inst
 python setup.py develop
 ```
 
-If you wish to are currently developing on mapnik-python and wish to change the code in place and immediately have python changes reflected in your environment.
+If you are currently developing on mapnik-python and wish to change the code in place and immediately have python changes reflected in your environment.
 
 
+```
+python setup.py install
+```
+
+If you wish to just install the package.
+
 ```
 python setup.py develop --uninstall
 ```
 
 Will de-activate the development install by removing the `python-mapnik` entry from `site-packages/easy-install.pth`.
 
 
+If you need Pycairo, make sure that PYCAIRO is set to true in your environment or run:
+
 ```
-python setup.py install
+PYCAIRO=true python setup.py develop
 ```
 
-If you wish to just install the package
-
 ## Testing
 
 Once you have installed you can test the package by running: