* Document how highlight updates works in the optimizing performance page - closes#360
* Change example animated gif to not mention Redux
* Be more explicit about the theory and workflow around using Highlight Updates - closes#360
* improve grammar, correctly label link to #avoid-reconciliation
* Trim content to its essentials and move to a more relevant place in Avoid Reconciliation section - Closes#360
* Make requested changes to wording and host images internally
* Minor rewording
