fixes #348 - misspelled github shortcut traceback...

In reference to Issue #348 

This is a first-draft, playing around (not a final fix - more of a debug instrumented experiment).

It doesn't seem to be in the coding style of the repo, but it does capture some parts of my playing around, in the comments - so I hope it will prove useful.

Right as it stands, if you use this, you get:
```
$ cookiecutter gh:aureyr/cookiecutter-pypackage.git
Username for 'https://github.com': yarko
Password for 'https://yarko@github.com': 
Error: the following failed (returned 128):
  git clone https://github.com/aureyr/cookiecutter-pypackage.git.git
```

which is a little more informative (not as noisy, no traceback).
I ended up leaving the `e.output` off, since it (at least for github) did not seem additionally useful,
always showing something about "user" regardless of where the typo was situated.

Comments?