colors/szakdark: provide better Error highlighting
colors/szakdark: ensure that the background is cleared for pythonDot

Otherwise, it looks goofy when printing.
colors/szakdark: tone down the indent guides so they're less distracting
colors/szakdark: make the git commit summary line standout a little more
user/jszakmeister: drop my color scheme alterations
Merge branch 'szakdark-updates' of https://github.com/jszakmeister/vimfiles
Document updates to szakdark colorscheme.