Fixes #839. Throw error if languages have same namespace

Also fix XTemplate & Riot.js

src/beautifiers/index.coffee

@@ -262,6 +262,12 @@ module.exports = class Beautifiers extends EventEmitter
       beautifiers = lang.beautifiers
       optionName = "language_#{lang.namespace}"
 
+      # Check if namespace has already been used
+      if _.has(flatOptions, "#{optionName}_disabled")
+        error = new Error("Language named '#{name}' has an already used namespace #{lang.namespace}.")
+        atom.notifications?.addError(error.message, {
+          stack: error.stack, detail: error.message, dismissable : true})
+        throw error
 
       # Add Language configurations
       flatOptions["#{optionName}_disabled"] = {

src/languages/riotjs.coffee

@@ -2,7 +2,7 @@ module.exports = {
 
   name: "Riot.js"
   description: "Riot.js HTML based templating language"
-  namespace: "html"
+  namespace: "riot"
   fallback: ['html', 'mustache']
 
   ###

src/languages/xtemplate.coffee

@@ -1,7 +1,7 @@
 module.exports = {
 
   name: "XTemplate"
-  namespace: "html"
+  namespace: "xtemplate"
   fallback: ['html','mustache']
 
   ###