Add missing catch blocks for migration from 1.1.1 to 1.2.0

Signed-off-by: Hugo Caloto <hcaloto@gmail.com>

lib/migrations/20160420180355-note-add-alias.js

@@ -7,6 +7,12 @@ module.exports = {
       return queryInterface.addIndex('Notes', ['alias'], {
         indicesType: 'UNIQUE'
       })
+    }).catch(function (error) {
+      if (error.message === "ER_DUP_FIELDNAME: Duplicate column name 'alias'") {
+        console.log('Migration has already run… ignoring.')
+      } else {
+        throw error
+      }
     })
   },