miscellaneous lint

Summary:
lint in miscellaneous files!

@joel you won this audit roulette!

Test Plan:

    ~/khan/devtools/khan-linter/runlint.py src/diffs/text-diff.jsx src/init.js src/perseus-markdown.jsx src/question-paragraph.jsx src/tex-wrangler.js src/util.js

See no lint errors in these files