Make staff debug info code to be always LTR

This fixes the code/debug content **Staff Debug Info** modal in RTL setups. The change is mostly a convenience change for the course staff and not something critical.

##Before (Unfixed)
![unfixed](https://cloud.githubusercontent.com/assets/645156/4752221/d8a61d34-5aa8-11e4-8f98-fd3b1cddaf00.png)

##After (Fixed)
![fixed](https://cloud.githubusercontent.com/assets/645156/4752219/d1f7f566-5aa8-11e4-9b23-7cac13b4f6d7.png)