Translation Crashes when ground truth output is not provided

[amrsharaf]

It seems like the current translation implementation assumes we always have access to the ground truth target translations (provided using the -tgt flag). This is not desirable when we don't have access to the ground truth target sentences.

[voidmagic]

I have fixed this, see #13 hope it will be help.

[guillaumekln]

This has been fixed.