fix(deisctl): Use $HOME/.deis/units, don't expand tilde (~) shortcut

The go func `user.Current()` returns error now that we build as a
static binary. Don't bother expanding ~ to $HOME, just use $HOME.
Merge pull request #94 from mboersma/fix-home-load-units

fix(deisctl): Use $HOME/.deis/units, don't expand tilde (~) shortcut