Cleanup CLI naming

Based on first review by @minrk

* bundlerextension for consistency
* Move CLI entry point into bundler package
* Add bundler/__main__.py

(c) Copyright IBM Corp. 2016

notebook/bundler/__main__.py

@@ -0,0 +1,7 @@
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+from .bundlerextensions import main
+
+if __name__ == '__main__':    
+    main()

notebook/bundler/bundlerextensions.py

@@ -3,8 +3,8 @@
 import sys
 import os
 
-from .nbextensions import (BaseNBExtensionApp, _get_config_dir)    
-from ._version import __version__
+from ..nbextensions import (BaseNBExtensionApp, _get_config_dir)
+from .._version import __version__
 
 from traitlets.config.manager import BaseJSONConfigManager
 from traitlets.utils.importstring import import_item

scripts/jupyter-bundlerextension

@@ -2,7 +2,7 @@
 # Copyright (c) Jupyter Development Team.
 # Distributed under the terms of the Modified BSD License.
 
-from notebook.bundlerextensions import main
+from notebook.bundler.bundlerextensions import main
 
 if __name__ == '__main__':
     main()

setup.py

@@ -180,7 +180,7 @@ if 'setuptools' in sys.modules:
             'jupyter-notebook = notebook.notebookapp:main',
             'jupyter-nbextension = notebook.nbextensions:main',
             'jupyter-serverextension = notebook.serverextensions:main',
-            'jupyter-bundler = notebook.bundlerextensions:main',
+            'jupyter-bundlerextension = notebook.bundler.bundlerextensions:main',
         ]
     }
     setup_args.pop('scripts', None)