Added test and updated docs

README.md

@@ -159,6 +159,14 @@ Responsible for loading the values parsed from `process.env` into the configurat
   // Can optionally also be an Array of values to limit process.env to.
   //
   nconf.env(['only', 'load', 'these', 'values', 'from', 'process.env']);  
+
+  //
+  // Can also specify a separator for nested keys (instead of the default ':')
+  //
+  nconf.env({
+    separator: '__',
+    filter: ['database__host', 'only', 'load', 'these', 'values', 'from', 'process.env']
+  });  
 ```
 
 ### Literal

test/fixtures/scripts/nconf-nested-env.js

@@ -0,0 +1,11 @@
+/*
+ * nconf-nested-env.js: Test fixture for env with nested keys.
+ *
+ * (C) 2012, Nodejitsu Inc.
+ * (C) 2012, Michael Hart
+ *
+ */
+ 
+var nconf = require('../../../lib/nconf').env({separator: '_'});
+
+process.stdout.write(nconf.get('SOME:THING'));

test/provider-test.js

@@ -60,6 +60,10 @@ vows.describe('nconf/provider').addBatch({
         script: path.join(fixturesDir, 'scripts', 'nconf-hierarchical-file-argv.js'),
         argv: ['--something', 'foobar'],
         env: { SOMETHING: true }
+      }),
+      "when 'env' is set to true with a nested separator": helpers.assertSystemConf({
+        script: path.join(fixturesDir, 'scripts', 'nconf-nested-env.js'),
+        env: { SOME_THING: 'foobar' }
       })
     }
   }