Version 0.5.0
Merge tag 'v0.5.0' into dev

Version 0.5.0 release

 * Add ``.drop()`` ``.collapse()`` methods to ``taxtastic.taxtable.TaxNode``
 * Change ``is_classified`` column in taxonomy database: now does not mark
   below species as unclassified if the species-level classification is valid. [GH-59]
 * Add ``taxit composition`` - shows the taxonomic composition of a reference package at a given rank
 * Fix broken ``taxit lonelynodes``
 * Add ``taxit merge`` - Identifies tax_ids which have been merged, suggests new tax_ids.
 * Add ``taxit add_to_taxtable`` - adds nodes to a taxonomy [GH-60]
 * Fix support for newer versions of PhyML [GH-61]
 * Updates for compatibility with RAxML 7.7.2
Release v0.5.1
bump version for development