examples using core.async

Something that could show off the capabilities of Clojure to learners is core.async, which would give a taste of how Clojure makes concurrency easier.

It should be possible to have multiple turtles acting independently in a canvas, similar Rich Hickey's ants demo (https://youtu.be/hb3rurFxrZ8?t=49m50s), although we only have atoms (no refs) in clojure-turtle because it is preferable to have the same code work the same in CLJS and Java Clojure.

This concept is very much like [NetLogo](https://ccl.northwestern.edu/netlogo/), for which there is already a set of materials built up around the concept.

Regardless of whether we attempt to create teaching materials that correspond to NetLogo, at least NetLogo would contain some nifty examples that are worth mimicking.

まずリポジトリに既存する例を確認し、次にリンクされた ants デモと NetLogo の資料を比較してアイデアを得てください。実装前に、具体的な例または教材のスコープを定義してください。done には、core.async を使用する複数の独立した turtles の有用なデモンストレーションを含める必要があります。

索引モデルが issue の本文から書いたものです。