Log stderr to console for git child processes to make debugging easier

This is related to Issue #204.  Logging stderr to console will help debug issues where the underlying git child process hangs.

Tested using the failing case outlined in #204 and confirmed output is the expected:
```
✓ twilio-meteor
    branch: http://github.com/andreioprisan/twilio-meteor.git#master
git clone stderr:  error: RPC failed; result=22, HTTP code = 405
```