[Java]: Clarify the primary goal of Aeron being performance on the readme.
[Java]: Clarify the primary goal of Aeron being performance on the readme.

galderz/Aeron,real-logic/Aeron,tbrooks8/Aeron,mikeb01/Aeron,real-logic/Aeron,mikeb01/Aeron,oleksiyp/Aeron,gkamal/Aeron,EvilMcJerkface/Aeron,EvilMcJerkface/Aeron,galderz/Aeron,tbrooks8/Aeron,oleksiyp/Aeron,gkamal/Aeron,real-logic/Aeron,EvilMcJerkface/Aeron,mikeb01/Aeron,gkamal/Aeron,oleksiyp/Aeron,EvilMcJerkface/Aeron,galderz/Aeron,real-logic/Aeron,galderz/Aeron,mikeb01/Aeron,tbrooks8/Aeron