Pass taxonomy to term class in Timber::handle_term_query

If two terms are defined with the same taxonomy, WP reuses the term (and term ID). TimberTerm will use the first one found, if it's not explicitly given. In handle_term_query, we have access to the full term object, so lets use it.
Merge pull request #145 from mgmartel/get-terms-taxonomy

Pass taxonomy to term class in Timber::handle_term_query