- allow only ``http|https`` links to be picked from scraped pages

hi, 

on some pages containing links to e.g. svn repos like this one: https://pypi.python.org/pypi/zope.sqlalchemy , devpi fails with an assertion error. 

i changed picking only ``http|https`` links as in the assertion. 

if you need something more, please let me know. 

best, andi