Convert to typescript

Rename typescript files to *.ts
Use typescript compiler instead of babel
Fix some type annotations
Remove @ import alias

Author: rotu

.eslintrc.js

@@ -10,8 +10,5 @@ module.exports = {
   rules: {
     'no-console': process.env.NODE_ENV === 'production' ? 'error' : 'off',
     'no-debugger': process.env.NODE_ENV === 'production' ? 'error' : 'off'
-  },
-  parserOptions: {
-    parser: 'babel-eslint'
   }
 }