Second attempt to make humanize_date() more deterministic

This reverts the first attempt (commit
8310b029), because relative dates in terms of
hours were printed.

This attempt passes the now object that we just created to humanize(), so that
will be used as a offset. If we don't supply that object, arrow will create a
different datetime object representing 'now', which might be slightly off
w.r.t. the now object we created.  Therefore the floating point arithmetic done
within the arrow library might not produce the desired results (delta / 86400).

By passing the offset ourselves I was able to produce reliable
results.

topydo/lib/Utils.py

@@ -113,5 +113,7 @@ def translate_key_to_config(p_key):
 
 def humanize_date(p_datetime):
     """ Returns a relative date string from a datetime object. """
-    return arrow.get(p_datetime).humanize().replace('just now', 'today')
+    now = arrow.now()
+    date = now.replace(day=p_datetime.day, month=p_datetime.month, year=p_datetime.year)
+    return date.humanize(now).replace('just now', 'today')