Error running joe -u on windows

[peterept]

C:\Work\Project>joe u
Updating gitignore files..
2017/02/16 16:22:20 open /tmp/master.zip: The system cannot find the path specified.

The reason is the my (and most) windows machines do not have a /tmp folder.
Easy enough to work around (by creating the c:\tmp folder).
But, a fix would be to change any hard coded references to /tmp to use os.TempDir() so it finds the correct temp folder for the O/S.

Thanks for such a great tool.

[jacekmusial]

I have opened pull request for that.
#102