Adding ESLint to help lint JSDoc comments

... In case anybody is interested in an ESLint vs JSHint debate.

We can tweak the .eslintrc rules to kill anything we don't want to enforce, or I can find the ESLint syntax to ignore specific rules per block/line since we're getting a few errors on long URLs in doc comments. :meh:

There isn't much reason to use both JSHint _**AND**_ ESLint, so we can probably remove the former if we want to go w/ ESLint.