Yellow vs Grey code

:warning: More opinions needed before merging :warning: 

Replaces the yellowish background of `inline code` and

```
Code Blocks
```

with a light grey background:

![grey](https://f.cloud.github.com/assets/378023/1670557/3e868646-5c9b-11e3-8108-7228658468db.png)

Current (yellow) vs new (grey):

![compare](https://f.cloud.github.com/assets/378023/1670561/4aafc7ac-5c9b-11e3-8962-01f59caa6741.png)

## Opinions

@segphault: Main voice behind removing yellow

@mikokim: Would like `inline code` without the border/background and only monospaced font. It's for easier scanning of the text.

@simurai Likes the yellow since it matches the syntax highlighting. Also makes it easier to see what is code and what is text.

Anyone more preferences?