Make UTF-8 badness go away

I don't deeply understand the details of what's UTF-8 and what encoding fails, but this fixed the following for me:

```
/Users/abesto/.rvm/gems/ruby-1.9.3-p484@global/gems/huffshell-0.0.14/lib/readers/history_reader.rb:60:in `split': invalid byte sequence in UTF-8 (ArgumentError)
	from /Users/abesto/.rvm/gems/ruby-1.9.3-p484@global/gems/huffshell-0.0.14/lib/readers/history_reader.rb:60:in `raw_lines'
	from /Users/abesto/.rvm/gems/ruby-1.9.3-p484@global/gems/huffshell-0.0.14/lib/readers/history_reader.rb:31:in `timestamps?'
	from /Users/abesto/.rvm/gems/ruby-1.9.3-p484@global/gems/huffshell-0.0.14/lib/readers/history_reader.rb:36:in `timestamps?'
	from /Users/abesto/.rvm/gems/ruby-1.9.3-p484@global/gems/huffshell-0.0.14/bin/huffshell:14:in `block in <top (required)>'
	from /Users/abesto/.rvm/gems/ruby-1.9.3-p484@global/gems/huffshell-0.0.14/bin/huffshell:12:in `each'
	from /Users/abesto/.rvm/gems/ruby-1.9.3-p484@global/gems/huffshell-0.0.14/bin/huffshell:12:in `<top (required)>'
	from /Users/abesto/.rvm/rubies/ruby-1.9.3-p484/bin/huffshell:23:in `load'
	from /Users/abesto/.rvm/rubies/ruby-1.9.3-p484/bin/huffshell:23:in `<main>'
	from /Users/abesto/.rvm/gems/ruby-1.9.3-p484/bin/ruby_executable_hooks:15:in `eval'
	from /Users/abesto/.rvm/gems/ruby-1.9.3-p484/bin/ruby_executable_hooks:15:in `<main>'
```