Revert "[FEATURE composable-computed-properties] Composable Computed Properties"

This reverts commit f34661cb86d1c359fdc2b1cc1b746c649b97e216.

Conflicts:
	features.json
	packages/ember-metal/lib/array.js
	packages/ember-metal/lib/computed.js
	packages/ember-metal/lib/enumerable_utils.js
	packages/ember-runtime/tests/computed/compose_computed_test.js