Add tljh-config command

We do not want users to hand-edit YAML files. This has been a
major source of bugs and confusion for users in z2jh. Doing so
in a terminal text editor makes it even worse.

This lets users type commands directly to modify config.yaml file
rather than edit files directly. This makes it a lot less error
prone and user friendly.

Advanced users can still edit config.yaml manually.

Fixes #38

setup.py

@@ -13,5 +13,10 @@ setup(
     install_requires=[
         'pyyaml==3.*',
         'ruamel.yaml==0.15.*'
-    ]
+    ],
+    entry_points={
+        'console_scripts': [
+            'tljh-config = tljh.config:main'
+        ]
+    }
 )