eles.classes impl + docs + test; closes #497
add batch pos for #509
don't check for dupes for perf.; closes #511
cache all dom dims where possible; use client dims

- use getBoundingClientRect()
- fixes #514
move edges (source, target) and nodes (parent)

closes #512 and #515
better scroll check for #514
improve cose & arbor; needs tweaking
updateMappers() not enough for data changes

fixes #521
improved & reviewed docs ported to 2.3
fix #528
fix #524
fix for descr in docs

Conflicts:
	documentation/index.html
Merge pull request #513 from prislop/patch-1

put child ele one level down the parent
comment out unfinished arbor improvement until finished
add nodes.commonAncestors(), eles.first(), eles.last(); test & document

closes #453
add edge.isSimple() & document

closes #527
cy.batch()

closes #534
sp
make arbor a bit easier to use with max sim time; unfix nodes on free; fixes #535
other minor arbor fixes