Links should have the same permissions as files in castle.

Let me know what you think. I'm looking to learn, so feel free to give me any suggestions you may have.

So you know, I couldn't chmod a symbolic link so I had to use umask to create the link with the correct permissions. Maybe I should add a comment to the code. I'm not sure if that is general knowledge.

I added a line to source the fs.sh file in the bats helper. I did so in order to gain access to the `octal_access` function in my tests. Let me know if there is a better way to do that.

Something else to note, I didn't handle the scenario where a file's access changes in git and the file is already linked. Should I add that to this PR or open a new issue?