Update partition-state.adoc

[azarboon]

I've read this section a few times and with due respect, I still don't get it. Especially, the bold part. Firstly, I thought it refers to scalability but then the "also" word in succeeding sentence told me I'm wrong. According to Reactive Manifesto, four main traits of Reactive Systems are: Responsive, Resilient, Elastic, Message-Driven. So, exactly which trait does the italic part is referring to? I believe it should be clearly stated.

Also, according to Glossary of Reactive Manifesto, partitioning of state helps with true isolation which helps with resiliency. I believe it should be added here for clarity. So, I've added it.

Distributed applications leverage parallelism of the underlying hardware by executing simultaneously on groups of computers that don't share memory. This parallel usage of multi-core servers brings the coordination and concurrency control challenge to the multi-machine level and makes the handling of state as a monolith inefficient and oftentimes impossible. Partitioning of state also helps with scalability: while each node can only store and process a finite dataset, a network of them can handle larger computational problems.