flip_leaves function added
donotrun  -> dontrun
scaler -> scalar
all_couple_rotations_at_k function added.
Added shuffle to the namespace.

Also added some doc to all_couple_rotations_at_k
There is some problem with match_order_dendrogram_by_old_order - might need to revisit this in the future...
untangle_forward_rotate_1side function added!
Rename: untangle_forward_rotate_1side -> untangle_step_rotate_1side

Also added the "direction" parameter (with either forward or backward)
Added k_seq and dend_heights_per_k to untangle_step_rotate_1side.
Vignettes doc for untangaling trees.
Version bump to 0.7