Timezone fix

[ostueker]

(Second try. )
As described in issue #48.
First commit adds test that demonstrates the issue:

HEAD is now at 6f29ffb... test for timezone issue
~/misc_projects/git-remote-hg/test $ make clean main.t 
rm -f -r 'trash directory'.* test-results
/bin/sh main.t 
ok 1 - setup
[...]
ok 34 - clone replace directory with a file
not ok 35 - timezone issues
#   
#       test_when_finished "rm -rf hgrepo gitrepo1 gitrepo2" &&
#   
[...]
#   
#       test_cmp expected_timestamp actual_timestamp
#   
# still have 3 known breakage(s)
# failed 1 among remaining 32 test(s)
1..35
make: *** [main.t] Error 1
~/misc_projects/git-remote-hg/test $ cat trash\ directory.main/tmp/*timestamp
Tue, 27 Sep 2016 00:20:00 -0210
Tue, 27 Sep 2016 00:00:00 -0230

The second commit introduces a change to fix it.