Initial attempt at optimizing chunk access.
More attempts to optimize decoding.
Try utf-8 and if not successful, auto detect when adjusting chunk for
proper decoding.
Merge branch 'master' into chunk-opt2

Conflicts:
	vlfi.el
Merge branch 'master' into chunk-opt2
Merge branch 'master' into chunk-opt2
Merge branch 'master' into chunk-opt2
Keep as much editing as possible when moving to intersecting chunk.
Add end character shift when adjusting chunk.  Apply partial chunk
update when buffer is not modified too.
Remove encode size bookkeeping.
Fix adjusting of end chunk bytes.
Merge branch 'master' into keep-edit

Conflicts:
	README.org
	vlfi.el
Add gitignore.
Minor adjustments:
- fix batch position formatting
- unconditionally update chunk on revert
- do nothing if same chunk is requested in `vlf-move-to-chunk'