Fix contenteditable in Firefox

This fixes #54. The issue was that we were doing

```js
return el.textContent || el.innerText;
```

Since el.textContent is falsey when it is an empty string it would
always try and return el.innerText. Firefox doesn't have this property
at all.
Properly formatted package.json

This adds the version number to the package.json so people can use Syn
with NPM. Fixes #53
Merge pull request #55 from matthewp/npm-pkg

Properly formatted package.json
Merge pull request #54 from matthewp/contenteditable

contenteditable not working in Firefox
Build for 0.0.3