Make improvements to edmtool (#454)

* DEV : edmtool improvements

- ensure that -h works along with --help
- add a new shell command

	modified:   ci/edmtool.py

* CLN : Use a dict literal instead of dict function

	modified:   ci/edmtool.py

ci/edmtool.py

@@ -152,7 +152,13 @@
 github_url_fmt = "git+http://github.com/enthought/{0}.git#egg={0}"
 
 
-@click.group()
+# Ensure that "-h" is supported for getting help.
+CONTEXT_SETTINGS = {
+    "help_option_names": ["-h", "--help"],
+}
+
+
+@click.group(context_settings=CONTEXT_SETTINGS)
 def cli():
     pass
 
@@ -234,6 +240,23 @@ def install(runtime, toolkit, pillow, environment, source):
     click.echo('Done install')
 
 
+@cli.command()
+@click.option('--runtime', default='3.6')
+@click.option('--toolkit', default='null')
+@click.option('--pillow', default='pillow')
+@click.option('--environment', default=None)
+def shell(runtime, toolkit, pillow, environment):
+    """ Create a shell into the EDM development environment
+    (aka 'activate' it).
+
+    """
+    parameters = get_parameters(runtime, toolkit, pillow, environment)
+    commands = [
+        "edm shell -e {environment}",
+    ]
+    execute(commands, parameters)
+
+
 @cli.command()
 @click.option('--runtime', default='3.6')
 @click.option('--toolkit', default='null')