Include alembic version scripts in built dist

MANIFEST.in

@@ -1,3 +1,4 @@
 include *.md
 include *.rst
 recursive-include rattail_quickbooks/db/alembic *.mako
+recursive-include rattail_quickbooks/db/alembic *.py

tasks.py

@@ -40,7 +40,7 @@ def release(c):
     """
     # rebuild local tar.gz file for distribution
     c.run('rm -rf rattail_quickbooks.egg-info')
-    c.run('python setup.py sdist --formats=gztar')
+    c.run('python -m build --sdist')
 
     filename = 'rattail-quickbooks-{}.tar.gz'.format(__version__)
     c.run('twine upload dist/{}'.format(filename))