`ReduceComputed` groups changed properties.

This is mostly important for sorting when items are changed via `setProperties`
instead of a sequence of `set`s.
fix nested yield
Merge pull request #3290 from hjdivad/array-computed-sort-via-sortProperties

`ReduceComputed` groups changed properties.
Typos and whitespace
IE indexOf fix again, this time without breaking every other browser
Merge pull request #3291 from lukemelia/ie-index-of-fix-moar-compat

IE indexOf fix again, this time without breaking every other browser
Version bump - v1.0.0
Fix ember-source to handle non-RCs
Fix size calculations on website
Contribution section added to README.md
reference CONTRIBUTING.md
Merge pull request #3292 from ysksn/master

Contribution section added to README.md