Move async-chan-wrapper into core.async
Fix test for enqueued puts inside async
Add if-closed (like not-found) for takes
Fix alt for if-closed
Move alt into impl ns to resolve privacy issues, add passing test
Merge remote-tracking branch 'tomjack/async-chans'
Merge remote-tracking branch 'tomjack/alt-privacy'
Merge remote-tracking branch 'tomjack/if-closed'

Conflicts:
	src/clj/core/async.clj
	test/core/async_test.clj