TEST (BK):  write_labels_to_annot with labels from only one hemisphere
FIX write_labels_to_annot():  with labels from only one hemisphere
ENH write_labels_to_annot():  hemi parameter

Option to save only one hemisphere
STY:  PEP 257
OPT TEST test_label:  copy only necessary fsaverage files
FIX:  use sample data instead of FreeSurfer data
Merge pull request #1504 from christianbrodbeck/annot

FIX Annot I/O