include 3dAFNItoNIFTI command in interfaces.afni
include AFNItoNIFTI in module init file
now able to set prefix and file extension automatically NIFTI
added hash_file protocol and dummy test file
added changelog information
Merge branch 'enh/afni2nifti'

Conflicts:
	CHANGES
	nipype/interfaces/afni/__init__.py
	nipype/interfaces/afni/preprocess.py