Fixed H3 to H4 tags, began rewrite of NP_0001

Some articles use level 3 headers tags but the stylesheet doesn't
display them right; changed to level 4 headers.

Started first pass of rewrite of NP_0001, and did a little more on
UT_0001
Added .DS_Store to .gitignore
Added newline to .gitignore
Removing .DS_Store