Bootstrap 3.0 moved to a "mobile first" approach. .container is really only there in instances where you need/want a boxy layout. but, if you exempt the div.container-fluid entirely, you're left with a fluid layout by default.
for example, to have a two-column fluid layout, simply use:
<body>
<header>...</header>
<div style="padding:0 15px;"><!-- offset row negative padding -->
<div class="row">
<div class="col-md-6">50%</div>
<div class="col-md-6">50%</div>
</div>
</div>
<footer>...</footer>
</body>
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