@mcbjam already gave this answer but here's a bit more explanation.
You can easily make the change using a media query in your CSS file without downloading BS. I just did this and it works beautifully.
The media query's "min-width" value will tell CSS to change the width of your container to 1000px only on screens larger than 1200px (or whatever width you choose to include there). This preserves the responsiveness of your site, so when the screen size jumps below that value (smaller monitor, tablet, smartphone, etc.), your site will still adjust to fit the smaller screens.
@media (min-width: 1200px) {
.container {
width: 1000px;
}
}