Prefix class names

[MAILPOET-1626]

assets/css/src/importExport.styl

@@ -76,12 +76,12 @@ span
     &.select2-search--dropdown
       display none !important
 
-.import_validation_step
+.mailpoet_import_validation_step
   max-width: 600px
   display: flex
   flex-direction: column
 
-  .import_step_buttons
+  .mailpoet_import_step_buttons
     flex-direction: row
     margin-top: 1.5em
 

assets/js/src/subscribers/importExport/previous_next_step_buttons.jsx

@@ -10,7 +10,7 @@ const PreviousNextStepButtons = ({ canGoNext, onPreviousAction, onNextAction })
     { 'button-disabled': !canGoNext },
   );
   return (
-    <div className="import_step_buttons">
+    <div className="mailpoet_import_step_buttons">
       <button
         className="button-primary wysija button"
         type="button"

assets/js/src/subscribers/importExport/step_input_validation.jsx

@@ -56,7 +56,7 @@ class StepInputValidation extends Component {
 
   render() {
     return (
-      <div className="import_validation_step">
+      <div className="mailpoet_import_validation_step">
         <label htmlFor="subscribers_agreed">
           <input
             type="checkbox"