Allowing import and py3 compatabillity

[borgr]

Hi,
The changes are not large and only affect the code (nothing in the logic is changed).

1. fixed a bug of not closing files
2. allowed to be run on py3
3. moved the main calculation into a function from main so import would be possible
4. PEP08
5. historical typo (BLEU instead of GLEU)
6. the name of the project is not so great at '-' can't be a part of a python module name, I would change it into a '_' if I were you, but its up to you.