Revert "removed byebug gem to development environment"

This reverts commit 36b96854e7375d7133522d5adb98c3276e2cbc61.
removed byebug gem to development environment for real this time.

resolve #5 (reverted from commit 41ce77791c5236f015582db7632c4068e0869266) (reverted from commit 36b96854e7375d7133522d5adb98c3276e2cbc61)