Release v2014.1.4 fix to git_pillar extra params

Fixes include changes to `salt.master.Master._clean_old_jobs`, `salt.pillar.git_pillar.GitPillar.__init__` and `salt.pillar.git_pillar.ext_pillar` functions.

The changes port git_pillar `Helium` changes into the v2014.1.4 release of salt:

```yaml
ext_pillar:
  - git: master git://github.com/crasiak/pillar_files.git root=pillars
```

Allowing users to specify pillars to be loaded from subdirectories of a git repository.