Convert prompt answers to lower case before checking

When prompting for yes/no answers, convert the answer to lower
case before comparing.  This makes it easier to catch answers
like "Yes", "yes", and "YES" with a comparison only for "yes".

Change-Id: I06da8281cec81a7438ebb46ddaf3344d12abe1eb
diff --git a/subcmds/init.py b/subcmds/init.py
index 48df9e8..99007d6 100644
--- a/subcmds/init.py
+++ b/subcmds/init.py
@@ -248,7 +248,7 @@
       print ''
       print 'Your identity is: %s <%s>' % (name, email)
       sys.stdout.write('is this correct [y/N]? ')
-      a = sys.stdin.readline().strip()
+      a = sys.stdin.readline().strip().lower()
       if a in ('yes', 'y', 't', 'true'):
         break