Make epm check and exit if patch isn't properly applied
Make epm check and exit if patch isn't properly applied

Use getProgramInvocationOutput instead of runProgramInvocation as it
will exit properly if the exit status is not ExitSuccess. A sample
contirved demo of it's behavior:

```
epm: Error: some packages failed to install:
old-time-1.1.0.3 failed while unpacking the package. The exception was:
user error ('/usr/bin/git' exited with an error:
git: 'applydfkja' is not a git command. See 'git --help'.)
```

Fixes #4.

typelead/epm,typelead/epm