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

Closes #555.

See https://jira.rax.io/browse/EOD-2
The "Account Info" text as the title? It should be easily overridden using the cascade. The reason I did it as a `:before` was just so including the `.account-info` div brought in the title as well, rather than requiring devs to implement more than one element/class to get the box to display properly like:
```
<div class="account-info">
    <h3>Account Info</h3>
    <p>Content in box</p>
</div>
```
I'm open to arguments for one over the other -- just explaining what caused me to choose the `:before` implementation.