Update README.rst

Author: PowderL

README.rst

@@ -50,8 +50,9 @@ At present, install ``forest-gis``  from wheel_ files are not provied for macOS.
 
 Build forest-gis from source
 ----------------------------
-Before you install the ``forest-gis`` from source, you need to update 
-cython_ for Windows and Linux to the newest version and then run ::
+Before you install the ``forest-gis`` from source, you need to first
+install or update cython_ for Windows and Linux to the newest version
+and then run ::
 
     pip install --verbose .