postpones elements destruction on `destroyFgSegs`
postpones execution of `updateHeight`
accepts multi-caching
adds the `splitRange` functionality
renders only the relevant events
caches non-requested events and only reports requested events
removes jQuery from `renderSegRow` (a skeleton that contains the segments)
starts attaching elements instead of strings
keeps track of the already cached events
wait for multiple range splits before rendering
fix to styling issues
Merge branch 'performance'