make_app uses threading.Lock now by default

Uses keyword arguments to use multiprocessing or uwsgi mixin. This
fixes an issue on exotic *BSDs such as NetBSD where Python comes not
with inter-process semaphores (issue 3307):

     mod_wsgi (pid=14365): Target WSGI script '/var/www/vhosts/my.hostname.org/htdocs/isso.wsgi' cannot be loaded as Python module.
     mod_wsgi (pid=14365): Exception occurred processing WSGI script '/var/www/vhosts/my.hostname.org/htdocs/isso.wsgi'.
     Traceback (most recent call last):
       File "/var/www/vhosts/my.hostname.org/htdocs/isso.wsgi", line 8, in <module>
         application = make_app(Config.load("/var/www/vhosts/my.hostname.org/htdocs/isso.cfg"))
       File "/usr/pkg/lib/python2.7/site-packages/isso/__init__.py", line 155, in make_app
         isso = App(conf)
       File "/usr/pkg/lib/python2.7/site-packages/isso/__init__.py", line 91, in __init__
         super(Isso, self).__init__(conf)
       File "/usr/pkg/lib/python2.7/site-packages/isso/core.py", line 223, in __init__
         self.lock = multiprocessing.Lock()
       File "/usr/pkg/lib/python2.7/multiprocessing/__init__.py", line 175, in Lock
         from multiprocessing.synchronize import Lock
       File "/usr/pkg/lib/python2.7/multiprocessing/synchronize.py", line 59, in <module>
         " function, see issue 3770.")
     ImportError: This platform lacks a functioning sem_open implementation, therefore, the required synchronization primitives needed will not function, see issue 3770.
replace isso module with isso.run