accounting is wrong on reload if tasks have a short (< 1 minute) interval

How to reproduce:

1. open gtimelog
2. Type 'started'
3. Wait for a few minutes
2. Type 'foo', press Enter
3. In a few seconds (before the minute in the system clock changes), type 'bar', press Enter
4. You'll see something like:

0 h 1 min (17:20-17:21) started
0 h 3 min (17:21-17:24) foo
0 h 0 min (17:24-17:24) bar

(that's the expected behavior)

5. Press Ctrl+R to reload timelog.txt
6. You'll now see:

0 h 1 min (17:20-17:21) started
0 h 3 min (17:21-17:24) bar
0 h 0 min (17:24-17:24) foo

(the ordering of 'foo' and 'bar' is reversed, and the time accounting is now wrong)

I don't mind having the precision of the accouting being just 1 minute, but the ordering shouldn't break on reload (it should always account the 'foo' task as taking a few minutes and the 'bar' task as taking 0 minutes).