Adding a unit converter

Due to issue #596 I coded a basic unit converter to convert time,
distance, mass, volume and digital values. It depends on node-units.

Also, fixed a typo.

modules/radio/strings.json

@@ -4,8 +4,7 @@
     },
     "now_playing": {
         "en": "Now Playing: {name} - {song} - {url}"
-    }
-    
+    },
     "request":{
     	"en":"{dj}: User {user} requests '{song}' to be played on tripradio."
     }

modules/units/README.md

@@ -0,0 +1,24 @@
+## Unit conversion
+
+Converts units into other units.
+
+### Description
+
+This module provides a command which allows users to convert units into another
+unit given the international character of networks. Converts time, distance,
+mass, volume and digital values.
+
+It has following dependencies:
+node-units : https://github.com/brettlangdon/node-units
+
+### Commands
+
+#### ~convert [input value] [input unit] to [output unit]
+
+Example:
+~convert 5 minutes to s
+~convert 20 quarts to gallons
+
+### TODO
+
+Currency Conversion

modules/units/strings.json

@@ -0,0 +1,8 @@
+{
+    "result": {
+        "en": "{input}: {output}"
+    },
+    "error": {
+        "en": "Something went wrong :( Example:'~convert 5 minutes to s'"
+    }
+}

modules/units/units.js

@@ -0,0 +1,33 @@
+/**
+ * Module Name: Unit Conversion
+ * Description: Converts units.
+ * Requires: node-units [https://github.com/brettlangdon/node-units]
+ * TODO: currency converting
+ */
+
+var _ = require('underscore')._,
+    unit = require('node-units');
+
+var units = function(dbot) {
+    	this.commands = {
+        	'~convert': function(event) {
+                var query = event.input[1];
+                try {
+                    event.reply(dbot.t('result', {
+                        'input': query,
+                        'output': result
+                    }));
+                    var result = unit.convert(query);
+                }
+            } catch (e) {
+                event.reply(dbot.t('error'));
+            }
+
+        }
+    };
+
+};
+
+exports.fetch = function(dbot) {
+    return new units(dbot);
+};

modules/units/usage.json

@@ -0,0 +1,3 @@
+{
+    "~convert": "~convert [input value] [input unit] to [output unit]"
+}