CSV humanize name option

CSVBuilder let's you pass in custom column names with a symbol or a string. However the name is always humanized on the generated CSV. If you want to parse the header with another tool, you may want to explicitly determine the column's name. This PR allows you to do that by passing `humanize_name` option to either `CSVBuilder`and `CSVBuilder#column`. It's important to notice that this is backwards compatible with the previous behavior.

closes #3096

Thanks @bonyiii and @vbalazs