Description of problem:
dnf can't be used to remove installed groups.

Version-Release number of selected component (if applicable):
0.4.1-1.git55e6369.fc21

How reproducible:
Always

Steps to Reproduce:
1.Try to remove some installed group with DNF

Actual results:
Fails with this backtrace:
Traceback (most recent call last):
  File "/bin/dnf", line 35, in <module>
    main.user_main(sys.argv[1:], exit_code=True)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 272, in user_main
    errcode = main(args)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 64, in main
    return _main(base, args)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 133, in _main
    result, resultmsgs = cli.run()
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 1290, in run
    return self.command.doCommand(self.base.basecmd, self.base.extcmds)
  File "/usr/lib/python2.7/site-packages/dnf/cli/commands.py", line 885, in doCommand
    return self.base.removeGroups(extcmds)
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 920, in removeGroups
    txmbrs = self.groupRemove(group_string)
  File "/usr/lib/python2.7/site-packages/dnf/yum/base.py", line 1583, in groupRemove
    txmbrs = self.remove(name=pkg, silence_warnings=True)
TypeError: remove() got an unexpected keyword argument 'name'

Expected results:
Successful resolve of dependencies and group remove.