Lightning Back Button

button_back.cmp

<aura:component implements="forceCommunity:availableForAllPageTypes" access="global">
  <aura:attribute name="wrapperClass" type="String" default="page-controls" />
  <aura:attribute name="buttonTitle" type="String" default="Go Back" />
  <div class="{!c.wrapperClass}">
    <button class="btn-hed btn-back" onclick="{!c.redirect}">{!c.buttonTitle}</button>
  </div>
</aura:component>

button_back.design

<design:component>
  <design:attribute name="wrapperClass" label="Wrapper CSS Class"/>
  <design:attribute name="buttonTitle" label="Button Title"/>
</design:component>

button_backController.js

({
  redirect: function (){
    var url = window.location.href; 
    var value = url.substr(0,url.lastIndexOf('/') + 1);
    window.history.back();
    return false;
  }
})