chroot does not backtrack if guard fails

[fimad]

If guard is used within the inner scraper passed to chroot scalpel should backtrack and try to find a tag that matches if the first tag fails. Currently this backtracking does not happen.

For example,

scrapeStringLike "<a>foo</a><a>bar</a><a>baz</a>" $ chroot "a" $ do
        t <- text Any
        guard ("b" `isInfixOf` t)
        html Any

Currently returns Nothing, but should return Just "<a>bar</a>"