Linting

This is an opinionated request, but since I found https://github.com/stevelacy/gulp-git/pull/11 via linting, I figured I'd make the offer. This sets up jshint, jscs, and editorconfig to match the code style in the repo. There's no enforcing mechanism right now, but if your editor is configured to work with any of these linting tools, they'll "do the right thing"™.