Beautiful colorbars and way more documentation!

Version 0.2.0

• Breaking: move rotate3D and flid3D function to freesurferformats. To update your code, replace fsbrain::rotate3D with freesurferformats::rotate3D.
• Support export of coloredmeshes to PLY format
• Add new vignette, a Frequently Askes Questions (FAQ) format
• Add R notebook with code and live examples (web)
• Improve documentation in docstrings
• Improve colormap computation and handling, especially drawing of colorbars
• Remove plyr dependendency, require freesurferformats 0.1.10
• The 'colormap' argument to all vis functions is deprecated, use makecmap_options instead. See the vis function docs for an example.