enh: first pass at the cifti2 reader

Author: satra

nibabel/__init__.py

@@ -63,6 +63,7 @@
                            apply_orientation, aff2axcodes)
 from .imageclasses import class_map, ext_map
 from . import trackvis
+from .cifti2 import parse_cifti_string
 
 # be friendly on systems with ancient numpy -- no tests, but at least
 # importable