Implement config.vim
Replace s:GetFormatterPattern() with new settings
Replace l:buftabs_marker_modified with new settings
Remove unused l:buftabs_separator setting
Replace highlihgt group variables with new settings
Replace g:buftabs_in_statusline with new settings
Replace marker variables with new settings
Move highlight-related stuff to config
Simplify s:list composition
Update readme with more settings
s0.21