Fix make output.

On some terminals make output shows escape codes instead of colorizing output.

For Example on konsole,

```
[bhush@archbox bootstrap]$ make
\n\n
\033[36mBuilding Bootstrap...\033[39m
033[37m--------------------------------------------------033[39m
Running JSHint on JavaScript...             \033[32m✔ Done\033[39m
Compiling LESS with Recess...               \033[32m✔ Done\033[39m
Prepping documentation assets...            \033[32m✔ Done\033[39m
Compiling and minifying JavaScript...       \033[32m✔ Done\033[39m
\033[37m--------------------------------------------------\033[39m
\033[36mSuccess!\n\033[39m
\033[37mThanks for using Bootstrap,
<3 @mdo and @fat\n\033[39m
```