update crawler to handle out of order listings

snapshots.l.o does't always list builds in a dependable order. For
example today's RFS's for nano are:

    100
    101
    76
    77

This makes the check fool-proof my doing a numerical comparision
diff --git a/crawler.py b/crawler.py
index 4498885..101995f 100755
--- a/crawler.py
+++ b/crawler.py
@@ -47,7 +47,7 @@
     '''
     # only analyze the last few builds
     links = list_links(url, r'<a\s*href=[\'|"](\d+)\/[\'"].*?>')[:limit]
-    for link in sorted(links, reverse=True):
+    for link in sorted(links, reverse=True, key=int):
         build = list_rfs('%s/%s' %(url, link))
         if build is not None:
             return (link, build)
@@ -63,4 +63,4 @@
             print "  %s: %s" % hwpack
 
     print "latest nano:"
-    print "  %s %s" % latest_rfs('http://snapshots.linaro.org/oneiric/linaro-o-nano')
+    print "  %s %s" % latest_rfs('http://snapshots.linaro.org/precise/images/nano')