get rid of the transaction.commit() in the models.appmaker function

[mmerickel]

This is using the wrong transaction manager and is unnecessary regardless as the transaction should not be committed mid-request.

related: Pylons/pyramid#3137

[stevepiercy]

Well, it was not as simple as deleting two lines:
https://github.com/Pylons/pyramid-cookiecutter-zodb/blob/latest/%7B%7Bcookiecutter.repo_name%7D%7D/%7B%7Bcookiecutter.repo_name%7D%7D/models.py#L12-L13

To reproduce, delete those two lines, then generate a project from the cookiecutter:

$ cookiecutter .

Accept the defaults, follow the generated README.txt, and visit the URL. Stack trace:

$ env/bin/pserve development.ini 
Starting server in PID 32405.
Serving on http://localhost:6543
Serving on http://localhost:6543
2017-07-25 20:29:03,737 ERROR [waitress:341][waitress] Exception when serving /
Traceback (most recent call last):
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/waitress/channel.py", line 338, in service
    task.service()
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/waitress/task.py", line 169, in service
    self.execute()
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/waitress/task.py", line 399, in execute
    app_iter = self.channel.server.application(env, start_response)
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/pyramid/router.py", line 270, in __call__
    response = self.execution_policy(environ, self)
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/pyramid_retry/__init__.py", line 134, in retry_policy
    return request.invoke_exception_view(reraise=True)
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/pyramid/view.py", line 755, in invoke_exception_view
    reraise_(*exc_info)
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/pyramid/compat.py", line 148, in reraise
    raise value
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/pyramid_retry/__init__.py", line 114, in retry_policy
    response = router.invoke_request(request)
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/pyramid/router.py", line 260, in invoke_request
    request._process_finished_callbacks()
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/pyramid/request.py", line 147, in _process_finished_callbacks
    callback(self)
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/pyramid_zodbconn/__init__.py", line 57, in finished
    primary_conn.transaction_manager.abort()
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/transaction/_manager.py", line 136, in abort
    return self.get().abort()
  File "/Users/stevepiercy/projects/pyramid-cookiecutter-zodb/pyramid_scaffold/env/lib/python3.6/site-packages/transaction/_manager.py", line 87, in get
    raise NoTransaction()
transaction.interfaces.NoTransaction