Fixes syntax error

[honshu]

No description provided.

[mibk]

Hello.

dupl uses Go 1.4 syntax where for range ... is a valid statement. There is a note in README about the minimal required version. Since it's only this statement that actually requires version 1.4 or above I'm thinking of accepting the PR provided you're in a situation that you can't use a newer version of Go and forking dupl doesn't work for you.

In case of accepting the PR I have some requirements about the code and commit message style.

1. The code must be gofmted!
2. There is a more simple notation: for _ = range ... (, _ can be omitted).
3. The commit message should start with a prefix, dupl: in this case, and should be in imperative mood (fix ..., change ...)
4. Vim exit shortcuts at the end of the commit message aren't preferred either.