change_logger.rb:80:in `index': invalid byte sequence in UTF-8 (ArgumentError)

Hi guys 

I had been using your gem, so in the las update (1.3) I found that [the last solution in encoding problem] (https://github.com/kebab-project/katip/issues/17) doesn't work in a little couple special cases, so based in this [stack overflow answer] (http://stackoverflow.com/posts/8873922/revisions) I had fixed it, please try and tell me it is working in your projects


```bash
$ katip
/usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/lib/katip/change_logger.rb:80:in `index': invalid byte sequence in UTF-8 (ArgumentError)
	from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/lib/katip/change_logger.rb:80:in `block in parse_change_log'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/lib/katip/change_logger.rb:76:in `each'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/lib/katip/change_logger.rb:76:in `parse_change_log'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/lib/katip/change_logger.rb:18:in `log_changes'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/bin/katip:14:in `<top (required)>'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/bin/katip:23:in `load'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/bin/katip:23:in `<main>'
```
Enforce encoding

```bash
$ LANG=utf-8 katip
/usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/lib/katip/change_logger.rb:80:in `index': invalid byte sequence in UTF-8 (ArgumentError)
	from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/lib/katip/change_logger.rb:80:in `block in parse_change_log'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/lib/katip/change_logger.rb:76:in `each'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/lib/katip/change_logger.rb:76:in `parse_change_log'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/lib/katip/change_logger.rb:18:in `log_changes'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/katip-1.3.0/bin/katip:14:in `<top (required)>'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/bin/katip:23:in `load'
	from /usr/local/rvm/gems/ruby-2.0.0-p247/bin/katip:23:in `<main>'
```