Fix for double quote parsing

Created by: juho-p

Problem: Fixes some weird backslash behavior

Solution: Changed parsing logic for backslash when in double quotes

Changes introduced by this pull request:

• tests
• changes to parser logic in words module

Other

Found some weird behaviour that I tried to fix hear. Seems you already have an issue here: https://github.com/redox-os/ion/issues/640

My changes try to make it work similar to bash. I had to change one test, which I believe is wrong ("\\n" should convert to "\n", not "\\n", both bash and fish behave this way).