Revert "Use of --filename option requires 2.5.0"

This reverts commit ac22058a63b8d18e95b3b5d0919577d32f554a80.
Revert "Merge pull request #46 from daumiller/master"

This reverts commit d6bd2e9aa22dc2f5df1cd2e43bdc3f709bac4cc6, reversing
changes made to 26e68c76e6ff6ce51f6f5ec875e8b130f762ef45.