Cleanups and fixes

Version 0.3.0

• Fix reading standard space data from template subjects other than fsaverage
• Add new cbry colormap and related mkco.cluster function, great for visualizing clusters
• Support pushing hemispheres apart to prevent overlapping inflated surfaces, fixes #7
• Remove rotate2D, flip2D, and readable.files functions, they have been moved to the freesurferformats package
• requires freesurferformats version >= 0.1.11 (up from 0.1.10)
• default to using rglot() as rgloptions parameter (instead of empty list) for vis functions, i.e., increase default plot resolution