Error-field styling not visible

[jdickey]

To demonstrate, fire up the app and click the "Add New Thing" button. Enter data for the fields, specifying an initial quantity of 0. When you hit the 'Submit' button, Rails wraps the invalid field (label and input control) in a div.field_with_errors (note the un-CSS-like underscores) element. Bootstrap knows nothing of this, apparently; it's incumbent upon us to define it.

This issue depends on both #5 (obviously) and #6.

[jdickey]

Nathan Tempelman on StackOverflow has an apparently useful solution to this, though why he uses a vendor prefix for WebKit is not immediately clear. I'd also prefer to use SCSS variables for the literals in his example, but they'd both compile down to the same thing in the asset pipeline.