Document requests library prereq.

README.md

diff --git a/README.md b/README.md
index 1ce19c6..19f7660 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,16 @@
 
 Each script also supports other flags.  Use --help to see them.
 
+# Prerequisites
+
+The client library requires
+[requests](http://www.python-requests.org/) to be installed.
+
+You can install it with `pip` or `easy_install`
+([instructions](http://www.python-requests.org/en/latest/user/install/))
+or install your operating system specific package.  On Ubuntu or
+Debian, it is in the `python-requests` package.
+
 # API Keys
 
 Organization Adminstrators can find their API key on their
@@ -18,4 +28,4 @@
 
 # Bugs/Support
 
-To report bugs, please email gci-support@google.com
+To report bugs, please email [gci-support@google.com](mailto:gci-support@google.com).