changed the code for git bug|feature|refactor to only accept single argument when not finishing a bug|feature|refactor.

Currently, when user will misspell the word __finish__ like below:

```
git bug finsih bugbranch
```

The code will create a branch named ``bug/finsih`` and check it out. This is not the expected behaviour and with the changes from this commit, after typing the code above, an error message will be given to the user:

```
too many arguments; if not finishing a bug, only <name> of new bug is expected
```