filling out config a little bit.

docs/config.rst

@@ -2,8 +2,13 @@
 Configuration
 =============
 
-Uranium provides infrastructure to pass in configuration variables, a
-common use case for a build framework with shared components:
+Uranium provides infrastructure to pass in configuration
+variables.
+
+Configuration variables are useful in a variety of situations, including:
+
+* choose whether to run in development mode
+* select the environment to run against
 
 .. code:: python
 

docs/cookbook/reuse.rst

@@ -110,3 +110,9 @@ And your consumer script will look like:
     import mycompany_build
     mycompany_build.setup(build)
     globals().update(get_public_directives())
+
+
+Caveats
+=======
+
+*

uranium/decorators.py

@@ -0,0 +1,2 @@
+def requires(func_name):
+    pass

uranium/environment_variables.py

@@ -29,6 +29,7 @@ def __getitem__(self, key):
 
             envvars["PYTHONPATH"]
         """
+        return os.environ[key]
 
     def generate_activate_content(self):
         """