add env() plugin

lib/eson.js

@@ -22,6 +22,7 @@ exports.version = '0.0.1';
  */
 
 exports.ms = require('./plugins/ms');
+exports.env = require('./plugins/env');
 exports.glob = require('./plugins/glob');
 exports.bools = require('./plugins/bools');
 exports.replace = require('./plugins/replace');

lib/plugins/env.js

@@ -0,0 +1,9 @@
+
+/**
+ * Allow environment variables to take precedence over `val`.
+ */
+
+module.exports = function(key, val){
+  var name = key.toUpperCase().split(' ').join('_');
+  return process.env[name] || val;
+};

test/bools.js

@@ -2,7 +2,7 @@
 var Parser = require('../')
   , bools = Parser.bools;
 
-describe('ms', function(){
+describe('bools', function(){
   it('should parse string bool representations', function(){
     bools('', 'yes').should.be.true;
     bools('', 'enabled').should.be.true;

test/env.js

@@ -0,0 +1,13 @@
+
+var Parser = require('../')
+  , env = Parser.env;
+
+describe('env', function(){
+  it('should allow setting environment variables', function(){
+    env('foo', 'bar').should.equal('bar');
+    process.env.FOO = 'baz';
+    env('foo', 'bar').should.equal('baz');
+    process.env.DEV_UI = 'yes';
+    env('dev ui', 'no').should.equal('yes');
+  })
+})