Vertical Rhythm: debug grid when $round-to-nearest-half-line is true

[edwardoriordan]

Loving the great vertical rhythm work in 0.13.alpha.

One thing I noticed was that when $round-to-nearest-half-line (which is a great feature!) is set to true the debug grid gets thrown off which

1. If I was trying it for the first time would make me thing it was broken.
2. can be hard to use to debug even if you know what is going on.

Simply halving the baseline that gets used in the baseline-grid-background will fix it. Something like

    @if $round-to-nearest-half-line {
      $baseline: $baseline/2;
    }

On a related note I wonder if compass should give an option to round to the nearest quater (not just the nearest half)? Would have to test to see how that works in practice with the new vertical rhythm work but in my experience quater of the line height is usually a good base line to work of for a vertical rhythm (see http://branch.com/b/baseline-grid-or-modular-scale-both-neither & http://aentan.com/design/new-visual-proportions-for-the-ios-user-interface for example)

Opinions? If people think it is a good idea am happy to submit a pull request