Adds an option for profiling builds

Thought it might be handy to see how long builds take.

Example
```shell
$ roto css profile
Host: DorkBook-Air.local
  Running "css" target...
  public/css/www/stylesheet.css
     + public/css/www/stylesheet.less
  public/css/www/embed.css
     + public/css/www/embed.less
  public/css/www/embed.player.css
     + public/css/www/embed.player.less
  public/css/www/anthem.css
     + public/css/www/anthem.less
  public/css/parents/stylesheet.css
     + public/css/parents/stylesheet.less
  public/css/admin/stylesheet.css
     + public/css/admin/stylesheet.less
  public/css/fonts.css
     + public/css/fonts.less
  public/css/fonts.gz.css
     + public/css/fonts.gz.less
  
Finished in 3.43s
```