Make positionUtils.getGrid private.
positionUtils.reset is only called by changeViewMode, not called by renderer.reset.
Do not calculate curve of relations at the initiation.
Create as invisible to prevent flash at the initiation.
Hide jsPlumb endpoints to prevent flash at the initiation.
Share the cache of position of grids by moving grids logic and creation and moving relations logic.
Make the positionCache private.
Extract Cache class.
Rename positionUtils to domPositionUtils.
Merge pull request #91 from pubannotation/refactor_cache_mechanism

Refactor cache mechanism