try breakpoints step by step, feature request

[slavugan]

for example I have such breakpoints

    breakpoints: [{
              width: 360, // max-width
              src: 'data-src-xsmall'
        }, {
              width: 600,
              src: 'data-src-small'
        }, {
              width: 1024,
              src: 'data-src-medium'
        }, {
              width: 1366,
              src: 'data-src-large'
        }]

it would be nice to have an option to try breakpoints one after one. for example if image doesn't have data-src-xsmall Blazy should check for data-src-small and so on.