Update VE core submodule to master (4c599b0)

Fix ContentBranchNode tests for getClientRects change.

New changes:
9bbd259 Create highlight elements on demand
a711c6d Indent demo HTML
b1b6562 Use cached surfaceView
d4b48b1 Replace <cite> with <span rel="ve:Alien">
ee5b697 Shields are dead, long live getClientRects
4c599b0 Remove repositionOnly argument from update

Change-Id: Ifa65c46d09864f214ece9349b990f7d8c07d416b