Try to load an app by name when mounts are empty

If a config file does not specify a mounts dictionary, greins will now
try to load the application by looking for a module whose name matches
the config file's name and looking for a symbol within called
'application' that is a callable WSGI handler.

This change means that developers can use this naming convention to
seamlessly import apps into greins without changing any files.

README.rst

@@ -54,9 +54,15 @@ are valid in these configuration files and work as in Gunicorn_. Other options,
 such as logging and worker configuration, are ignored and should be configured
 globally for the Greins application.
 
+As a convenience, a file name ``myapp`` which does not define any ``mounts``
+will try to import ``myapp:application`` and mount it underneath the path
+``/myapp``.
+
 It should be possible to write an application for Gunicorn_ and then place
-the application's configuration inside the configuration directory for Greins
-to begin using it within Greins immediately.
+a Gunicorn_ configuration file inside the configuration directory for Greins
+to begin using it within Greins immediately, provided that the config file name
+matches a module in the python path which exports ``application`` as a WSGI_
+callable.
 
 Examples
 ++++++++

greins/app.py

@@ -8,6 +8,7 @@
 
 from gunicorn.app.wsgiapp import WSGIApplication
 from gunicorn.config import make_settings
+from gunicorn.util import import_app
 
 from greins.reloader import Reloader
 from greins.router import Router
@@ -88,6 +89,11 @@ def load_file(self, cf):
             self.logger.info("Loading configuration for %s" % cf_name)
             execfile(cf, cfg, cfg)
 
+            # By default, try to mount the application by name
+            if not cfg['mounts']:
+                app_name, ext = os.path.splitext(os.path.basename(cf))
+                cfg['mounts'][app_name] = import_app(app_name)
+
             # Load all the mount points
             for r, a in cfg['mounts'].iteritems():
                 # Capture the handler in a closure