style(rxApp): Add styles and documenation for Account Info box

Closes #555.

See https://jira.rax.io/browse/EOD-2
An argument for not hard-coding it here is that we'll likely be making use of this through a directive. 

So a dev won't be writing a div with this class directly, but instead doing something like `<rx-account-info></rx-account-info>`. This directive would take the responsibility for putting the title in the div.