Comment explaining that contributors.html is a fallback.

This file would seem to be the source for /contributors, but actually
it's a fallback for /website/content/tmpl/contrib.html.

Add a comment explaining the automatic generation to avoid confusion
for folks attempting to edit the website.

Also rename the template to contributing.html for consistency.

Change-Id: Ic98c494b0cc24292dac8a4a22c751aded87f5b48

website/content/contributors.html

@@ -1,3 +1,6 @@
+<!-- NOTE: this file is a fallback in case automatic generation of
+     contributors list fails. See /website/tmpl/contributors.html -->
+
 <h1>Contributors</h1>
 
 <p>Camlistore contributors include:</p>

website/contributors.go

@@ -100,7 +100,7 @@ func gitShortlog() *exec.Cmd {
 }
 
 func genContribPage() ([]byte, error) {
-	contribHTML := readTemplate("contrib.html")
+	contribHTML := readTemplate("contributors.html")
 
 	// The same committers could've authored commits with different emails/usersnames.
 	// We index the authors by name and by email to try and merge graphs connected by