Remove readIfExists

See http://nodejs.org/api/fs.html#fs_fs_exists_path_callback

Quote: "In particular, checking if a file exists before opening it is an anti-pattern that leaves you vulnerable to race conditions: another process may remove the file between the calls to fs.exists() and fs.open(). Just open the file and handle the error when it's not there."
Merge pull request #23 from DieBuche/readIfExists

Remove readIfExists