* Bump `eslint-plugin-react`
* Add `eslint-config-xo-react`
* Add XO
* Remove eslint-related dependencies, add XO config and use XO as the linter
* Code style: Standard => XO ✨
* Use xo property to ignore files
* Fix remaining errors
* Step 1: move electorn into `app/`.
This is to comply with the suggested directory format of
`electron-builder`: https://github.com/electron-userland/electron-builder#two-packagejson-structure
* Step 2: add build directory with icon files for mac / windows
* Step 3: move all development (web) assets into main directory
* Step 4: add `build` namespace to dev `package.json`
* Step 5: move all dev dependencies into dev file and get rid of
old electron packagers in favor of `eletorn-builder`
* Step 6: target build inside `app/` as everything else is excluded at build time
* Step 7: remove old stuff!
* Step 8: update README
* turn off asar for `child_pty`
