:field_seperator option is being ignored

You're using `update` to set a default for the `:field_seperator` option. This, however, also overwrites the options passed to csv2yaml or yaml2csv. You should use this:

```ruby
options.merge!(:field_separator => ',') unless options.has_key?(:field_seperator)
```

Also, `ya2yaml` seems to be a bit outdated or something. The YAML generated looked really bad. You should consider just using `.to_yaml`. Works way better in my case. :)