show help when circli is run with default params in non-git repo

[mcgaffin]

If I run circli without options in a non-git repo, I get this:

circli
fatal: not a git repository (or any of the parent directories): .git
** (MatchError) no match of right hand side value: {"", 128}
    (circli) lib/circli/util.ex:36: Circli.Util.git_config_dir/0
    (circli) lib/circli/util.ex:49: Circli.Util.git_repo_info/0
    (circli) lib/circli/circle2_api.ex:154: Circli.Circle2Api.print_build_summary/1
    (elixir) lib/kernel/cli.ex:105: anonymous fn/3 in Kernel.CLI.exec_fun/2

Instead, I should see help text, as if I ran: circli --help