Working version for static content & editor.
Fixes & cleanup.

* Declared function instead of adding them to `window` of isolated scope.
* Fixed support for custom indentation sizes.
* Using latest commit SHA whenever we can find it to avoid improper caching of editorconfig.
Added manifest files to repo.
Added icons.
window -> global for more browserify-way
Minor fixes and manifest updates.
Add `private: true` to prevent publishing to npm.
Added support for global default editorconfig.

Removed extra dev directory.
Simplified build step.
Minor fix.
Add explanation.
Fixed viewer being inserted after `setEditorConfig`.
Added title to options page.
Using MutationObserver instead of long-polling.

Seems to be the most reliable way to track GitHub page changes.