Japanese version of the manifesto

This is Japanese version of the reactive manifesto, but the *glossary* will be translated later.

[こちら](http://typesafe.com/blog/reactive-manifesto-20)で

> The other nuance is replacing Scalable with Elastic. I think this adjustment should make sense to most readers familiar with modern workload patterns.  Truly Reactive Systems should react to changes in the input rate by increasing or decreasing the resources allocated to service these inputs, **not just expanded according to its usage (which is the definition of Scalable)**.

とおっしゃってるので、「伸縮性」の方が @jboner さんの意図をよく表しているかなと思ってこっちにしてみたのですが、どちらの方が良いでしょうか…。個人的には弾力性でも良いと思います。