Adding function to synchronize term/taxonomy IDs

When saving/updating Scriblio authority posts, the `scrib-authority` meta data should be verified to ensure the values are accurate for the site the plugin is activated on.  This is valuable when ingesting posts and the meta data contains IDs from another site.

See #17
Rename sync_term to sanitize_term

* Check by ID before failing over to checking for the accuracy of a term by slug
* Sanitize primary_term when post meta is retrieved for a given post
* Hook into the WordPress importer in order to hijack the postmeta and fix scrib-authority data if necessary

See #17
Sanitize parent and child terms too.

Also leveraging `update_post_meta` method to handle sanitization of terms
Merge pull request #18 from borkweb/17-sync-terms

Adding function to synchronize term/taxonomy IDs