add css.map files to .gitignore

I dont' want to ignore the entire stylesheets directory, since I don't
always want to write things in sass or convert other's files.
clean up style.css
customize left nav per subsection

having a link to 'all posts' on anything other than the blog doesn't
make sense. rather than put a conditional here it's nice that each
subsection can customize it with a partial.
update the color scheme

to match my current favorite colors (and hair) I've gone with a
blue/teal color scheme. shout outs to paletton.com for an amazing color
scheme creator.