typo in trait name of AFNI CatMatvec interface

[salma1601]

Summary

typo in afni.Catmatvec: trait name is fourxfour not fourXfour
https://github.com/nipy/nipype/blob/master/nipype/interfaces/afni/utils.py#L610

Actual behavior

from nipype.interfaces import afni

cat_matvec = afni.CatMatvec()
cat_matvec.inputs.oneline = True

throws

AttributeError: 'CatMatvecInputSpec' object has no attribute 'fourXfour'

Platform details:

Please paste the output of: python -c "import nipype; print(nipype.get_info()); print(nipype.__version__)"

{'nibabel_version': '2.1.0', 'sys_executable': '/home/salma/anaconda2/bin/python', 'networkx_version': '1.11', 'numpy_version': '1.13.1', 'sys_platform': 'linux2', 'sys_version': '2.7.13 |Anaconda custom (64-bit)| (default, Dec 20 2016, 23:09:15) \n[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)]', 'commit_source': u'repository', 'commit_hash': '7ead69d', 'pkg_path': 'nipype', 'nipype_version': u'1.0.0-dev+g7ead69d', 'traits_version': '4.6.0', 'scipy_version': '0.19.1'}
1.0.0-dev+g7ead69d