BF: Fixing path issues for CMTK Parcellate dilated ROI files

Addresses #591 

Some cleanup of the CMTK Parcellate interface to fix the weird output issues introduced by the dilated fMRI ROIs.

Seems that the

    op.join(op.curdir, "blah"...

wasn't working properly. Just replaced it with:

    op.abspath("blah")

and removed some unused variables.

Tested with:

    import nipype.interfaces.cmtk as cmtk
    import os
    import nipype.pipeline.engine as pe          # pypeline engine
    a = pe.Node(interface=cmtk.Parcellate(), name="testparc")
    a.base_dir = "testparcnode"
    a.inputs.subject_id = "bert"
    a.inputs.subjects_dir = os.environ["SUBJECTS_DIR"]
    a.inputs.dilation = False
    a.inputs.parcellation_name = "scale33"
    a.run()

There shouldn't be any differences in outputs for the other parcellation scales.

Should give a report.rest with inputs/outputs like this (github markdown seems to hide < undefined >):

Original Inputs
---------------

* dilation : True
* freesurfer_dir : <undefined>
* ignore_exception : False
* out_roi_file : <undefined>
* parcellation_name : scale33
* subject_id : bert
* subjects_dir : /Applications/freesurfer/subjects

Execution Inputs
----------------

* dilation : True
* freesurfer_dir : <undefined>
* ignore_exception : False
* out_roi_file : <undefined>
* parcellation_name : scale33
* subject_id : bert
* subjects_dir : /Applications/freesurfer/subjects

Execution Outputs
-----------------

* aseg_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc/aseg.nii.gz
* cc_unknown_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc/cc_unknown.nii.gz
* dilated_roi_file_in_structural_space : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc/ROIv_HR_th.nii.gz
* ribbon_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc/ribbon.nii.gz
* roi_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc/ROI_scale33.nii.gz
* roi_file_in_structural_space : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc/ROI_HR_th.nii.gz
* roiv_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc/ROIv_scale33.nii.gz
* white_matter_mask_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc/fsmask_1mm.nii.gz


# For no Dilation:

Original Inputs
---------------

* dilation : False
* freesurfer_dir : <undefined>
* ignore_exception : False
* out_roi_file : <undefined>
* parcellation_name : scale33
* subject_id : bert
* subjects_dir : /Applications/freesurfer/subjects

Execution Inputs
----------------

* dilation : False
* freesurfer_dir : <undefined>
* ignore_exception : False
* out_roi_file : <undefined>
* parcellation_name : scale33
* subject_id : bert
* subjects_dir : /Applications/freesurfer/subjects

Execution Outputs
-----------------

* aseg_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc_nodil/aseg.nii.gz
* cc_unknown_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc_nodil/cc_unknown.nii.gz
* dilated_roi_file_in_structural_space : <undefined>
* ribbon_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc_nodil/ribbon.nii.gz
* roi_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc_nodil/ROI_scale33.nii.gz
* roi_file_in_structural_space : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc_nodil/ROI_HR_th.nii.gz
* roiv_file : <undefined>
* white_matter_mask_file : /Users/erik/Dropbox/Testing/testparc/testparcnode/testparc_nodil/fsmask_1mm.nii.gz