git ignore /bin correctly (#3737)
git ignore /bin correctly (#3737)

This fixes /bin showing up when created as a symlink and avoids accidentally ignoring unrelated folders called "bin" elsewhere in the repository.
Simran-B/arangodb,fceller/arangodb,fceller/arangodb,graetzer/arangodb,fceller/arangodb,wiltonlazary/arangodb,wiltonlazary/arangodb,Simran-B/arangodb,Simran-B/arangodb,arangodb/arangodb,fceller/arangodb,wiltonlazary/arangodb,fceller/arangodb,arangodb/arangodb,arangodb/arangodb,arangodb/arangodb,arangodb/arangodb,graetzer/arangodb,Simran-B/arangodb,graetzer/arangodb,Simran-B/arangodb,graetzer/arangodb,wiltonlazary/arangodb,graetzer/arangodb,wiltonlazary/arangodb,wiltonlazary/arangodb,Simran-B/arangodb,graetzer/arangodb,wiltonlazary/arangodb,fceller/arangodb,graetzer/arangodb,graetzer/arangodb,Simran-B/arangodb,fceller/arangodb,Simran-B/arangodb,fceller/arangodb,graetzer/arangodb,Simran-B/arangodb,graetzer/arangodb,graetzer/arangodb,graetzer/arangodb,fceller/arangodb,wiltonlazary/arangodb,arangodb/arangodb,fceller/arangodb,arangodb/arangodb,arangodb/arangodb,graetzer/arangodb,Simran-B/arangodb,graetzer/arangodb