Bootstrap Integration

This gem integrates the bootstrap gem for the Bootstrap v4 CSS and JS assets.

We don't alter anything about the Bootstrap JS. As Bootstrap requires, we require jQuery, popper.js, and the bootstrap.js libraries.

We do, however, make a few alterations to the Bootstrap CSS. Firstly, we darken the default blue, red, yellow, and green colors by 8%. Next, we change the warning theme color to use orange instead of yellow, and we change the info theme color to use purple instead of light-blue. Finally, we alter how the badge component renders, to have a light colored background with a darker colored text, which is more color accessible. There are a few other tiny changes (e.g. darkening the breadcrumb divider color, removing margins from <p>s inside of .alerts, etc). But none of these changes negate any of the Bootstrap documentation; they simply mean that there will be some small visual changes here and there.