api: Document options required for use with Zulip Enterprise.

(imported from commit 59f136cf0f1a5d9509bec054b060ab44695b77e0)

README.md

@@ -31,9 +31,14 @@ file is as follows:
     key=<api key from the web interface>
     email=<your email address>
 
+If you are using Zulip Enterprise, you should also add
+
+    site=<your Zulip Enterprise server's URI>
+
 Alternatively, you may explicitly use "--user" and "--api-key" in our
 examples, which is especially useful if you are running several bots
-which share a home directory.
+which share a home directory.  There is also a "--site" option for
+setting the Zulip Enterprise server on the command line.
 
 You can obtain your Zulip API key, create bots, and manage bots all
 from your Zulip [settings page](https://zulip.com/#settings).

zulip/__init__.py

@@ -47,8 +47,8 @@ API_VERSTRING = "v1/"
 def generate_option_group(parser):
     group = optparse.OptionGroup(parser, 'API configuration')
     group.add_option('--site',
-                      default=None,
-                      help=optparse.SUPPRESS_HELP)
+                     help="Zulip Enterprise server URI (if using Zulip Enterprise)",
+                     default=None)
     group.add_option('--api-key',
                      action='store')
     group.add_option('--user',