Add logo for Gush to help

                   
|Q            |A  |
|---          |---|
|Bug Fix?     |n  |
|New Feature? |y  |
|BC Breaks?   |n  |
|Deprecations?|n  |
|Tests Pass?  |y  |
|Fixed Tickets|   |
|License      |MIT|
|Doc PR       |   |
                   


 Sent using [Gush](https://github.com/gushphp/gush)
good initial logo, there is a service that perhaps can help to improve it? http://picascii.com/ ?

also why not just call it EOF? for the delimiters, anyone knows the history of these?