jshint to eslint conversion

[newtewt]

We are beginning to use eslint everywhere and replacing jshint. Adding this ticket as a tracking point to convert jshint code to use eslint.

[kennsippell]

From #186:

• Enable "curly": "error", in .eslintrc
• Enable "guard-for-in": "error", in .eslintrc
• eslint-disable-line no-useless-escape in csv-to-docs.js
• eslint-disable-next-line no-buffer-constructor in attachment-from-file.js

[garethbowen]

This has been done for a while.