Add user photos to codeblocks

[alexandersimoes]

Whenever we show a list of codeblocks it would be great to show the user's photo associated with it. Below are some details on what this would mean:

• [x] Add faker avatar images to db for our test fake users (@alexandersimoes)
• [ ] Add images to CodeBlockCard (@davelandry)
• [ ] Add images to snippet Dialog window (@davelandry)