Rather than using the following to append the word "Login" and "Menu"
content: "Login";
content: "Menu";
Remove them from the CSS code and use the following HTML markup:
<button type="button" id="login-btn" class="navbar-toggle" data-toggle="collapse">
<i class="fa fa-user"></i> LOGIN
</button>
<button type="button" id="menu-btn" class="navbar-toggle" data-toggle="collapse">
MENU <i class="fa fa-bars"></i>
</button>
Here is a JSFiddle to show you: http://jsfiddle.net/vkEb6/