chan-benchmark now uses the Channels framework.

…and becomes slower.
Removed (via commenting) the need for logging.swift in Channels.
Benchmarking, two ways.

And a big revision of the go benchmark.
Unit tests
A linking change in Xcode 6.1 means command-line tools don't work (easily) with frameworks.

The command-line tools were changed accordingly.
Fix a copy-paste oversight in two test cases.
Overrode send() specifically for SingletonChan.

SingletonChan can have a simplified version of send(), since only one send operation can succeed.
Also, the BufferedChan implementation had a potential race condition which could have allowed a second message through for SingletonChan.
Attempting to work around issues when overriding computed properties in Chan and subclasses.
Updated chan.swift and chan-pthreads.swift with recent changes from master.