block data without a tree

[jameshadfield]

At the moment there's a (very slow and incorrect) method by which blocks are drawn if a tree is not present. www.github.com/jameshadfield/JScandy/js/canvas/gubbins/trim_blocks.gubbins.js

This should be made much faster by either moving it to www.github.com/jameshadfield/JScandy/js/stores/Taxa_Locations.js (where y values are queried from anyway), or by having a precomputed function in the gubbins code. This will have to fall back to our old way of calculating a block for every leaf as the concept of blocks at nodes doesn't make sense without a tree.

For labelling purposes we could create a flat tree from the taxa in the block file? Thoughts @richardgoater @jyothishnt

[jameshadfield]

As of commit 1c95dcf we don't display gubbins blocks unless there is a tree

If you can think of a sensible way to display the blocks without a tree then this issue is for you