Modified the verbose scroll bar on code view should not be displayed.

Thank you for providing the cool theme.

When I described the long sentence on the code view, verbose scroll bar was appeared.
Because you define `overflow-x: auto` where `figure.code.highlight` and `figure.code.td.code`.
```scss
figure.code{
        // ...
        .highlight{
                overflow-x: auto;
        }
        // ...
        td.code{
                width: 100%;
                padding-left: 15px;
                overflow-x: auto;
        }
}
```
So, I removed the definition `overflow-x: auto`.

* before
![before](https://cloud.githubusercontent.com/assets/1687203/3159370/bc5ae988-eb0f-11e3-9e45-638ecc2656a4.png)

* after
![after](https://cloud.githubusercontent.com/assets/1687203/3159372/c234ed86-eb0f-11e3-97e1-72a9746fe6ed.png)