Show the age of a repository in the index, via javascript

This patch adds the age of the repository to the index view, using javascript
to give a nice human string for the age.

When javascript is not available, the element remains hidden.

Signed-off-by: Alberto Bertogli <albertito@blitiri.com.ar>
Work around HTTPError status code issues

It turned out that bottle.py is not backwards-compatible with the status code
change: older versions encode the status in e.status; newer ones use
e.status_code (and e.status became a string).

This patch works around that by trying to pick up which of the two variants we
have, and deciding accordingly.

Signed-off-by: Alberto Bertogli <albertito@blitiri.com.ar>