support uu encoding

fixes #755 

@jeremy @bf4 @mikel 
perhaps we want to a add a strip_heredoc helper (not monkey patch!) if we do this a lot?https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/string/strip.rb#L22

```ruby
  # Technically, it looks for the least indented line in the whole string, and removes
  # that amount of leading whitespace.
  def strip_heredoc
    indent = scan(/^[ \t]*(?=\S)/).min.try(:size) || 0
    gsub(/^[ \t]{#{indent}}/, '')
  end
```