Fix line number CSS Bug

The changes in this pull request aim to fix issue #4 and to fix issue #10.

In this pull request, I chose to set the width on the pre tag inline.  Given my setup, I found that the width (in pixels) of the pre element needs to be 8 times the number of digits in the largest number we are trying to display.

I will now show a series of screenshots that capture the changes this pull request will result in.

## Screenshots

### Current Issue

![testing_syntax_highlighting___grumpyrainbow com-3](https://f.cloud.github.com/assets/1584123/1609900/0ba1bd0a-5560-11e3-948c-12c0239c21c8.png)

### With Changes [line="1"]

![testing_syntax_highlighting___grumpyrainbow com-2](https://f.cloud.github.com/assets/1584123/1609908/5278b508-5560-11e3-8254-c62939231eb8.png)

### With Changes [line="1000"]

![testing_syntax_highlighting___grumpyrainbow com-4](https://f.cloud.github.com/assets/1584123/1609915/90b7b5d0-5560-11e3-808c-20a754b1b974.png)

## Comments

This is just one way of handling this problem.  If you have other ideas, I'm open to hearing them.

Take care!