themes/gitstatus: Fix where it shows extra a space

For example, if $HOME is not a git repository, it should show:

    ~>

But previously it incorrectly showed:

    ~ >

This commit makes it aware of such case, inserting the space
accordingly instead of always adding a space.
themes/gitstatus: $SSH_CONNECTION could've spaces
Merge pull request #75 from godfat/theme-git-status-fix

themes/gitstatus: Fix where it shows extra a space