Add a domReady implementation.

Add explicit peer dependencies for wire domready.
Add a minimal loader extension to map "domReady!" to an empty module that resolves when the dom is ready.
Update version.
Change load extension to actually work.

Unfortunately, I had to change the strategy:
1. There's no way to remap a module name across packages.
2. All of the hooks are required so that the loader doesn't attempt to locate, fetch, and translate a "domReady!" module.
Go back to a simpler set of hooks -- just instantiate -- and override "wire/domReady" instead of "domReady!".
Stop fetching the actual "wire/domReady" module file.
Provide noops for other unused loader hooks to reduce potential unnecessary processing.
Merge pull request #3 from unscriptable/domready

Add a domReady implementation.