We moved off to our own fork of velocity many moons ago to fix
a memory leak bug when velocity was being barely maintained. They
have now merged the bugfix, so go back to mainline.
The velociraptor was only actioning hidden -> visible transitions
if the position had changed, so the one RR that stayed in position
but became visible... didn't become visible.
We are no longer allowed to stick random properties on child properties, and
the Velociraptor animations were causing some React warnings.
Move the startStyles and enterTransitionOpts properties up to the Velociraptor
node, and avoid setting arbitrary props on the created children. This is less
flexible, as it assumes that all children will have the same start style;
however, we weren't using the flexibility, and we can always replace the array
with a map or a function or something if we need it in the future.
1) Correct fix for Velociraptor (we need to find the DOM node and pass that in)
2) Do the same leak fix for the read marker
3) Update the dependency to our fork which is fixed to make the call we do to release memory actually work.
4) Remove the velocity-ui-pack dependency which is unnecessary because velocity-ui is included in the velocity package
* handle having a single child, rather than an array of children
* Correctly animate children which are added at the same time as the
Velociraptor, rather than added afterwards
* Set the child to hidden at the end of the initial animation, if that is
required by the style property.
