Centers buttons, left-aligns all text, improves overall left-margin and padding.

This is a big update for the styling of the content of the page.  Not
everything is perfect and it may never be.  At this point, I've targeted
things down generically basically as best as possible, but some things
still look bad.  I'm marking TODOs #9 and #15 as done for now.  They
will have to be revisited and changed in the future on a case-by-case
basis.