improve perfomance

[Sproute777]

https://github.com/Sproute777/a_star/tree/feature/a_star_for_tbs

change Offset to Point , no needed to translate toDouble and back, no needed to use floor and etc.

[RafaelBarbosatec]

Great! I will appreciate so much a PR with your contribution.

[Sproute777]

for check

• items.any() items.contains() more faster then items.where, items.firstWhere

• for (var item in items) more faster then items.forEach();

indexWhere useful for check item and using it next;

[RafaelBarbosatec]

Thanks so much for this tips. I will implement this improvements.

[Sproute777]

resolve and merge with 0.3.1 ready for review added benchmark in example