Add button class to older version of Rainmaker Design Templates.

custom.css

.button {
-webkit-transition:all .2s ease-in-out;
-moz-transition:all .2s ease-in-out;
-ms-transition:all .2s ease-in-out;
-o-transition:all .2s ease-in-out;
transition:all .2s ease-in-out;
background-color:#00a99d;
border:0;
border-radius:3px;
color:#fff;
cursor:pointer;
font-size:18px;
font-weight:400;
letter-spacing:1px;
padding:20px;
text-transform:uppercase;
-webkit-font-smoothing:antialiased
}

.button:hover {
background-color:#00baad;
color:#fff
}

.entry-content .button:hover {
color:#fff
}