first attempt to port to Polymer 1.0

[triglian]

Hi, this is a first attempt to bring the ace-element to the Polymer 1.0 world.

Some things to notice:

• Prefixed all private methods with _ to match the Polymer style guide.
• Added basic documentation.
• I have to check if the editor exists at every <property>changed handler since somehow Polymer calls them very early (I think earlier than the dummy editor we setup to avoid just this). Let me know if I am missing something.
• Moved demo.html to demo/index.html
• Adapted index.html to use <iron-component-page>
• I wasn't able to find an equivalent for templateContent() in Polymer 1.0 so I inject the theme styles directly to the element. Let me know if I should do this differently.
• There is no onMutation in Polymer 1.0 so I setup a MutationObserver to do the work.

Looking forward to your feedback.