Add support for importing taxonomy via CSV.

[monfresh]

This allows categories to be created in a tree structure supported by the ancestry gem. To see an example of a valid CSV file that recreates the Open Eligibility taxonomy, look at data/taxonomy.csv

For more details about how taxonomy works, read our Wiki article on taxonomy basics:
https://github.com/codeforamerica/ohana-api/wiki/Taxonomy-basics

Special thanks to @volkanunsal for the feature request and getting this work started.

[coveralls]

Coverage increased (+0.01%) when pulling 030acc8 on taxonomy-import into b733c26 on master.

[volkanunsal]

Awesome. Just one question. Does parent_id refer to the taxonomy_id or record id? If it's the former, then perhaps something like parent_taxonomy_id might be a better choice to avoid database errors due to bad record id during the import process, since parent_id is implemented by ancestry gem, and I don't know how well it might play with that gem.

[monfresh]

Calling it parent_id versus parent_taxonomy_id will not make any difference during the import. It would only be a semantic difference. parent_id is only used to look up the parent Category in the database. It's not an attribute that gets written. Did you run into database errors due to a bad record id?

[volkanunsal]

I'll let you know soon. The problems I ran into so far were mass-assignment not allowed errors on parent_name and parent_id fields.

[monfresh]

You can ignore those errors. It's just letting you know that parent_name and parent_id were passed in as attributes, but were not actually written because they are not permitted. I could remove those attributes from the hash before passing them on, but the end result would be the same (minus the non-user facing errors in the log).

[monfresh]

Note that you would also see the same mass-assignment warnings regardless of what the column is called, unless you remove them from the hash before passing them on.

[volkanunsal]

Here is an error I've been getting:

Ancestry::AncestryException: No child ancestry for new record. Save record before performing tree operations.

[volkanunsal]

This is where the error originates.

[volkanunsal]

Figured out that there was an error in creating the parent category, which was suppressed because it's not created with a bang.