Inject-Lite

[jakobo]

Create a version of Inject that doesn't support IE7 anymore.

• inject.js
  • uses window.postMessage if easyXDM isn't available
  • no longer includes easyXDM in the default build
• relay.html
  • like inject.js no longer uses easyXDM, but postMessage
• inject-ie7.js
  • includes easyXDM library for cross domain
• relay-ie7.html
  • includes easyXDM library for cross domain

This will break backcompat in the current proposed state. Alternatively, we could create as "lite", but I believe our long term goal should be to remove IE7 support.