resolves problem with various date length (issue #317)

I had created a fix to resolve the problem when the date format is of variable length.  I had tested with different dates, and it is working fine.  
I am using the same date format as specified in issue #317 
  "timeformat": "%A, %d %b %Y, %H:%M",


$ jrnl 2014-01-22: test0-1
[Entry added to default journal]

$ jrnl --short
Wednesday, 22 Jan 2014, 09:00 test0-1
Saturday, 06 Dec 2014, 06:31 test1
Saturday, 06 Dec 2014, 06:31 test2
Saturday, 06 Dec 2014, 06:36 test3

$ jrnl 2014-01-22: test0-2
[Entry added to default journal]

$ jrnl 2014-04-22: test0-2
[Entry added to default journal]

$ jrnl --short
Wednesday, 22 Jan 2014, 09:00 test0-1
Wednesday, 22 Jan 2014, 09:00 test0-2
Tuesday, 22 Apr 2014, 09:00 test0-2
Saturday, 06 Dec 2014, 06:31 test1
Saturday, 06 Dec 2014, 06:31 test2
Saturday, 06 Dec 2014, 06:36 test3
$