Fix typo in getFile.

I have very limited experience in Node, but it looks to me like `fs.readFile('args.file', …` would try to read a file named "args.file", instead of a file name located in `args.file`, which I assume was what you intended.

Please ignore if I have made a mistake.
Merge pull request #1 from rosspenman/patch-1

Fix typo in getFile