Adding support for calling spectral.py from outside source directory.

I found that calling spectral from outside the source directory threw errors opening the text files. 

```$ python spectral-installer/spectral.py 
Traceback (most recent call last):
  File "spectral-installer/spectral.py", line 7, in <module>
    with open('processes.txt') as f:
IOError: [Errno 2] No such file or directory: 'processes.txt'```

(I also just wanted to submit my first pull request on something.)