app/views/user_mailer/welcome_email.html.erb
<h1>Welcome to apibootstraper.com, <%= @user.username %></h1>
<p>
You have successfully signed up to apibootstraper.com,
your username is: <%= @user.username %>.<br/>
</p>
<p>
To login to the site, just follow this link: <%= @url %>.
</p>
<p>Thanks for joining and have a great day!</p>