fixing config functionality, adding documentation.

docs/config.rst

@@ -0,0 +1,27 @@
+=============
+Configuration
+=============
+
+Uranium provides infrastructure to pass in configuration variables, a
+common use case for a build framework with shared components:
+
+.. code:: python
+
+    # config.defaults can be used to set some defaults.
+    build.config.set_defaults({
+        "development": "false"
+    })
+
+    def test(build):
+        # one can set development mode by adding a -c development=true before the directive:
+        # ./uranium -c development=true test
+        if build.config["development"].startswith("t"):
+            build.packages.install(".", develop=True)
+
+
+------------------
+Full API Reference
+------------------
+
+.. autoclass:: uranium.config.Config
+    :members: set_defaults

docs/index.rst

@@ -47,6 +47,7 @@ Contents:
    installation
    tutorial
    examples
+   config
    envs
    executables
    history

docs/managing_packages.rst

@@ -2,7 +2,7 @@
 Managing Packages
 =================
 
-Any configuration related to packages is done through the Packages object. Here's an example showing some of the more
+Any configuration related to packages is done through the Packages object. Here is an example showing some of the more
 common operations:
 
 .. code:: python

uranium/scripts/main.py

@@ -1,7 +1,7 @@
 """Uranium, a build system for python
 
 Usage:
-  uranium [-p <build_file> -v]
+  uranium [-p <build_file> -v -c <confarg>...]
   uranium [-p <build_file> -v -c <confarg>...] <directive> [DIRECTIVE_ARGS ...]
   uranium [-p <build_file> -v] --directives
   uranium (-h | --help)
@@ -10,6 +10,7 @@
   -h, --help        show this usage guide
   -v, --verbose     show verbose output
   -p <build_file>, --path <build_file>  the build file to use.
+  -c <confarg>,  --confarg <confarg> a configuration value to set.
   --directives      list all the directives available in a build file.
   <directive>       the directive to execute (defaults to "main")
 
@@ -54,7 +55,7 @@ def main(argv=sys.argv[1:]):
     if options["--directives"]:
         build_options.override_func = _print_directives
 
-    config = parse_confargs(options['<confgarg>'])
+    config = parse_confargs(options['-c'])
     build = Build(root, config=config, with_sandbox=True)
     try:
         return build.run(build_options)