Colorize output

Attached is the updated Revel code base with Colored output. Some things that need to be addressed before any merge.

- Is there a place we check if we're in Windows? If so I need to toggle disable this whole library (just a 1-liner hopefully).
- Currently I only color the first bit of text, the message types (DEBUG,WARN,ERROR,TRACE) and any arguments. for example:

```go
  variable := "this"
  ERROR.Println("I don't color this, but I do color %s", ERROR_COLOR(variable))
```
- It would be pretty simple to allow the user to specify colors in the config, I'm not sure if we want to do this at all? For now the colors are: Trace - Magenta, Info - Green, Warn - Yellow, Error - Red, Header - Blue
- The hardest part about my approach to coloring variables, is that we need to continue to do it in the future. It's a very manual process. (The message type will always color)